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 $87.90   6.654%   $93.7489   $93.75   $93.75   $93.70  
  Purchase #2 $218.71   11.865%   $244.6599   $244.66   $244.65   $244.70  
  Purchase #3 $204.56   5.295%   $215.3915   $215.39   $215.40   $215.40  
  Purchase #4 $83.85   5.169%   $88.1842   $88.18   $88.20   $88.20  
  Purchase #5 $152.99   11.709%   $170.9036   $170.90   $170.90   $170.90  
  Purchase #6 $149.38   5.302%   $157.3001   $157.30   $157.30   $157.30  
  Purchase #7 $234.40   4.736%   $245.5012   $245.50   $245.50   $245.50  
  7 purchase totals = $1,131.79       $1,215.6894   $1,215.68   $1,215.70   $1,215.70