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 $195.41   3.362%   $201.9797   $201.98   $202.00   $202.00  
  Purchase #2 $200.41   11.695%   $223.8479   $223.85   $223.85   $223.80  
  Purchase #3 $211.27   7.803%   $227.7554   $227.76   $227.75   $227.80  
  Purchase #4 $41.76   9.215%   $45.6082   $45.61   $45.60   $45.60  
  Purchase #5 $146.39   7.791%   $157.7952   $157.80   $157.80   $157.80  
  Purchase #6 $155.77   9.522%   $170.6024   $170.60   $170.60   $170.60  
  Purchase #7 $245.79   11.464%   $273.9674   $273.97   $273.95   $274.00  
  7 purchase totals = $1,196.80       $1,301.5562   $1,301.57   $1,301.55   $1,301.60