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 $216.52   8.525%   $234.9783   $234.98   $235.00   $235.00  
  Purchase #2 $49.28   4.263%   $51.3808   $51.38   $51.40   $51.40  
  Purchase #3 $35.64   5.168%   $37.4819   $37.48   $37.50   $37.50  
  Purchase #4 $98.58   12.164%   $110.5713   $110.57   $110.55   $110.60  
  Purchase #5 $151.65   11.805%   $169.5523   $169.55   $169.55   $169.60  
  Purchase #6 $228.61   12.208%   $256.5187   $256.52   $256.50   $256.50  
  Purchase #7 $95.65   12.735%   $107.831   $107.83   $107.85   $107.80  
  7 purchase totals = $875.93       $968.3143   $968.31   $968.35   $968.40