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 $98.97   4.564%   $103.487   $103.49   $103.50   $103.50  
  Purchase #2 $113.30   11.376%   $126.189   $126.19   $126.20   $126.20  
  Purchase #3 $229.61   9.816%   $252.1485   $252.15   $252.15   $252.10  
  Purchase #4 $242.53   5.196%   $255.1319   $255.13   $255.15   $255.10  
  Purchase #5 $101.63   11.206%   $113.0187   $113.02   $113.00   $113.00  
  Purchase #6 $34.99   5.106%   $36.7766   $36.78   $36.80   $36.80  
  Purchase #7 $61.26   8.668%   $66.57   $66.57   $66.55   $66.60  
  7 purchase totals = $882.29       $953.3217   $953.33   $953.35   $953.30