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 $62.42   11.592%   $69.6557   $69.66   $69.65   $69.70  
  Purchase #2 $97.74   4.347%   $101.9888   $101.99   $102.00   $102.00  
  Purchase #3 $131.90   4.746%   $138.16   $138.16   $138.15   $138.20  
  Purchase #4 $162.59   12.762%   $183.3397   $183.34   $183.35   $183.30  
  Purchase #5 $157.88   3.257%   $163.0222   $163.02   $163.00   $163.00  
  Purchase #6 $40.78   12.603%   $45.9195   $45.92   $45.90   $45.90  
  Purchase #7 $231.47   13.815%   $263.4476   $263.45   $263.45   $263.40  
  7 purchase totals = $884.78       $965.5335   $965.54   $965.50   $965.50