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 $67.96   9.532%   $74.4379   $74.44   $74.45   $74.40  
  Purchase #2 $116.87   11.169%   $129.9232   $129.92   $129.90   $129.90  
  Purchase #3 $59.95   3.862%   $62.2653   $62.27   $62.25   $62.30  
  Purchase #4 $117.74   3.140%   $121.437   $121.44   $121.45   $121.40  
  Purchase #5 $24.80   5.422%   $26.1447   $26.14   $26.15   $26.10  
  Purchase #6 $61.40   6.385%   $65.3204   $65.32   $65.30   $65.30  
  Purchase #7 $16.84   3.478%   $17.4257   $17.43   $17.45   $17.40  
  7 purchase totals = $465.56       $496.9542   $496.96   $496.95   $496.80