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 $39.55   5.222%   $41.6153   $41.62   $41.60   $41.60  
  Purchase #2 $189.32   5.297%   $199.3483   $199.35   $199.35   $199.30  
  Purchase #3 $237.98   10.312%   $262.5205   $262.52   $262.50   $262.50  
  Purchase #4 $225.75   12.823%   $254.6979   $254.70   $254.70   $254.70  
  Purchase #5 $48.36   13.653%   $54.9626   $54.96   $54.95   $55.00  
  Purchase #6 $230.93   12.189%   $259.0781   $259.08   $259.10   $259.10  
  Purchase #7 $230.27   5.304%   $242.4835   $242.48   $242.50   $242.50  
  7 purchase totals = $1,202.16       $1,314.7062   $1,314.71   $1,314.70   $1,314.70