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 $71.94   9.584%   $78.8347   $78.83   $78.85   $78.80  
  Purchase #2 $225.92   4.166%   $235.3318   $235.33   $235.35   $235.30  
  Purchase #3 $86.95   5.207%   $91.4775   $91.48   $91.50   $91.50  
  Purchase #4 $223.92   13.287%   $253.6723   $253.67   $253.65   $253.70  
  Purchase #5 $125.99   6.245%   $133.8581   $133.86   $133.85   $133.90  
  Purchase #6 $184.39   5.692%   $194.8855   $194.89   $194.90   $194.90  
  Purchase #7 $132.42   3.385%   $136.9024   $136.90   $136.90   $136.90  
  7 purchase totals = $1,051.53       $1,124.9623   $1,124.96   $1,125.00   $1,125.00