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 $87.28   11.823%   $97.5991   $97.60   $97.60   $97.60  
  Purchase #2 $205.28   7.662%   $221.0086   $221.01   $221.00   $221.00  
  Purchase #3 $36.74   13.335%   $41.6393   $41.64   $41.65   $41.60  
  Purchase #4 $201.52   11.287%   $224.2656   $224.27   $224.25   $224.30  
  Purchase #5 $148.54   12.844%   $167.6185   $167.62   $167.60   $167.60  
  Purchase #6 $170.78   10.322%   $188.4079   $188.41   $188.40   $188.40  
  Purchase #7 $180.80   7.644%   $194.6204   $194.62   $194.60   $194.60  
  7 purchase totals = $1,030.94       $1,135.1594   $1,135.17   $1,135.10   $1,135.10