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 $57.56   7.681%   $61.9812   $61.98   $62.00   $62.00  
  Purchase #2 $126.69   10.716%   $140.2661   $140.27   $140.25   $140.30  
  Purchase #3 $235.54   13.502%   $267.3426   $267.34   $267.35   $267.30  
  Purchase #4 $93.57   4.872%   $98.1287   $98.13   $98.15   $98.10  
  Purchase #5 $208.62   12.592%   $234.8894   $234.89   $234.90   $234.90  
  Purchase #6 $179.46   13.327%   $203.3766   $203.38   $203.40   $203.40  
  Purchase #7 $159.66   6.763%   $170.4578   $170.46   $170.45   $170.50  
  7 purchase totals = $1,061.10       $1,176.4424   $1,176.45   $1,176.50   $1,176.50