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 $67.47   9.209%   $73.6833   $73.68   $73.70   $73.70  
  Purchase #2 $212.45   11.375%   $236.6162   $236.62   $236.60   $236.60  
  Purchase #3 $132.66   5.701%   $140.2229   $140.22   $140.20   $140.20  
  Purchase #4 $93.89   4.689%   $98.2925   $98.29   $98.30   $98.30  
  Purchase #5 $146.76   7.405%   $157.6276   $157.63   $157.65   $157.60  
  Purchase #6 $141.51   9.865%   $155.47   $155.47   $155.45   $155.50  
  Purchase #7 $159.25   9.479%   $174.3453   $174.35   $174.35   $174.30  
  7 purchase totals = $953.99       $1,036.2578   $1,036.26   $1,036.25   $1,036.20