Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $164.51   11.692%   $183.7445   $183.74   $183.75   $183.70  
  Purchase #2 $172.66   12.341%   $193.968   $193.97   $193.95   $194.00  
  Purchase #3 $210.75   13.634%   $239.4837   $239.48   $239.50   $239.50  
  Purchase #4 $172.48   3.678%   $178.8238   $178.82   $178.80   $178.80  
  Purchase #5 $151.84   5.831%   $160.6938   $160.69   $160.70   $160.70  
  Purchase #6 $190.83   12.133%   $213.9834   $213.98   $214.00   $214.00  
  Purchase #7 $183.77   11.850%   $205.5467   $205.55   $205.55   $205.50  
  7 purchase totals = $1,246.84       $1,376.2439   $1,376.23   $1,376.25   $1,376.20