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 $43.79   5.866%   $46.3587   $46.36   $46.35   $46.40  
  Purchase #2 $86.72   11.759%   $96.9174   $96.92   $96.90   $96.90  
  Purchase #3 $91.53   11.299%   $101.872   $101.87   $101.85   $101.90  
  Purchase #4 $231.72   5.221%   $243.8181   $243.82   $243.80   $243.80  
  Purchase #5 $198.76   12.292%   $223.1916   $223.19   $223.20   $223.20  
  Purchase #6 $13.83   3.673%   $14.338   $14.34   $14.35   $14.30  
  Purchase #7 $144.67   3.322%   $149.4759   $149.48   $149.50   $149.50  
  7 purchase totals = $811.02       $875.9717   $875.98   $875.95   $876.00