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 $60.81   3.118%   $62.7061   $62.71   $62.70   $62.70  
  Purchase #2 $124.92   5.622%   $131.943   $131.94   $131.95   $131.90  
  Purchase #3 $6.30   5.715%   $6.66   $6.66   $6.65   $6.70  
  Purchase #4 $162.86   4.307%   $169.8744   $169.87   $169.85   $169.90  
  Purchase #5 $216.48   8.326%   $234.5041   $234.50   $234.50   $234.50  
  Purchase #6 $246.42   3.252%   $254.4336   $254.43   $254.45   $254.40  
  Purchase #7 $145.76   9.583%   $159.7282   $159.73   $159.75   $159.70  
  7 purchase totals = $963.55       $1,019.8494   $1,019.84   $1,019.85   $1,019.80