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 $43.62   7.759%   $47.0045   $47.00   $47.00   $47.00  
  Purchase #2 $188.26   7.325%   $202.05   $202.05   $202.05   $202.10  
  Purchase #3 $57.31   4.268%   $59.756   $59.76   $59.75   $59.80  
  Purchase #4 $221.92   11.681%   $247.8425   $247.84   $247.85   $247.80  
  Purchase #5 $170.52   8.166%   $184.4447   $184.44   $184.45   $184.40  
  Purchase #6 $188.83   6.117%   $200.3807   $200.38   $200.40   $200.40  
  Purchase #7 $24.98   4.874%   $26.1975   $26.20   $26.20   $26.20  
  7 purchase totals = $895.44       $967.6759   $967.67   $967.70   $967.70