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 $58.51   4.736%   $61.281   $61.28   $61.30   $61.30  
  Purchase #2 $86.98   12.581%   $97.923   $97.92   $97.90   $97.90  
  Purchase #3 $228.62   4.625%   $239.1937   $239.19   $239.20   $239.20  
  Purchase #4 $68.26   10.433%   $75.3816   $75.38   $75.40   $75.40  
  Purchase #5 $57.28   4.243%   $59.7104   $59.71   $59.70   $59.70  
  Purchase #6 $183.62   4.180%   $191.2953   $191.30   $191.30   $191.30  
  Purchase #7 $37.34   10.280%   $41.1786   $41.18   $41.20   $41.20  
  7 purchase totals = $720.61       $765.9636   $765.96   $766.00   $766.00