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 $184.91   5.232%   $194.5845   $194.58   $194.60   $194.60  
  Purchase #2 $96.29   5.499%   $101.585   $101.59   $101.60   $101.60  
  Purchase #3 $66.58   8.512%   $72.2473   $72.25   $72.25   $72.20  
  Purchase #4 $73.98   12.118%   $82.9449   $82.94   $82.95   $82.90  
  Purchase #5 $210.77   11.696%   $235.4217   $235.42   $235.40   $235.40  
  Purchase #6 $183.43   8.288%   $198.6327   $198.63   $198.65   $198.60  
  Purchase #7 $164.96   9.153%   $180.0588   $180.06   $180.05   $180.10  
  7 purchase totals = $980.92       $1,065.4749   $1,065.47   $1,065.50   $1,065.40