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 $207.71   7.846%   $224.0069   $224.01   $224.00   $224.00  
  Purchase #2 $227.95   7.813%   $245.7597   $245.76   $245.75   $245.80  
  Purchase #3 $190.58   11.332%   $212.1765   $212.18   $212.20   $212.20  
  Purchase #4 $63.35   5.245%   $66.6727   $66.67   $66.65   $66.70  
  Purchase #5 $99.40   5.581%   $104.9475   $104.95   $104.95   $104.90  
  Purchase #6 $65.48   6.442%   $69.6982   $69.70   $69.70   $69.70  
  Purchase #7 $219.92   5.525%   $232.0706   $232.07   $232.05   $232.10  
  7 purchase totals = $1,074.39       $1,155.3321   $1,155.34   $1,155.30   $1,155.40