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 $119.66   10.351%   $132.046   $132.05   $132.05   $132.00  
  Purchase #2 $206.68   3.229%   $213.3537   $213.35   $213.35   $213.40  
  Purchase #3 $153.90   5.773%   $162.7846   $162.78   $162.80   $162.80  
  Purchase #4 $184.72   5.675%   $195.2029   $195.20   $195.20   $195.20  
  Purchase #5 $247.66   4.768%   $259.4684   $259.47   $259.45   $259.50  
  Purchase #6 $148.45   11.851%   $166.0428   $166.04   $166.05   $166.00  
  Purchase #7 $224.95   11.312%   $250.3963   $250.40   $250.40   $250.40  
  7 purchase totals = $1,286.02       $1,379.2947   $1,379.29   $1,379.30   $1,379.30