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 $78.44   4.469%   $81.9455   $81.95   $81.95   $81.90  
  Purchase #2 $116.75   7.626%   $125.6534   $125.65   $125.65   $125.70  
  Purchase #3 $212.85   10.541%   $235.2865   $235.29   $235.30   $235.30  
  Purchase #4 $78.70   4.632%   $82.3454   $82.35   $82.35   $82.30  
  Purchase #5 $6.51   6.376%   $6.9251   $6.93   $6.95   $6.90  
  Purchase #6 $58.56   9.224%   $63.9616   $63.96   $63.95   $64.00  
  Purchase #7 $128.61   8.762%   $139.8788   $139.88   $139.90   $139.90  
  7 purchase totals = $680.42       $735.9963   $736.01   $736.05   $736.00