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 $60.98   4.124%   $63.4948   $63.49   $63.50   $63.50  
  Purchase #2 $187.71   7.248%   $201.3152   $201.32   $201.30   $201.30  
  Purchase #3 $107.39   3.717%   $111.3817   $111.38   $111.40   $111.40  
  Purchase #4 $25.79   13.152%   $29.1819   $29.18   $29.20   $29.20  
  Purchase #5 $43.91   3.462%   $45.4302   $45.43   $45.45   $45.40  
  Purchase #6 $190.50   7.543%   $204.8694   $204.87   $204.85   $204.90  
  Purchase #7 $45.95   9.429%   $50.2826   $50.28   $50.30   $50.30  
  7 purchase totals = $662.23       $705.9558   $705.95   $706.00   $706.00