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 $191.67   9.545%   $209.9649   $209.96   $209.95   $210.00  
  Purchase #2 $158.25   8.656%   $171.9481   $171.95   $171.95   $171.90  
  Purchase #3 $32.42   8.131%   $35.0561   $35.06   $35.05   $35.10  
  Purchase #4 $167.55   7.440%   $180.0157   $180.02   $180.00   $180.00  
  Purchase #5 $101.85   8.439%   $110.4451   $110.45   $110.45   $110.40  
  Purchase #6 $192.26   5.680%   $203.1804   $203.18   $203.20   $203.20  
  Purchase #7 $208.74   3.375%   $215.785   $215.79   $215.80   $215.80  
  7 purchase totals = $1,052.74       $1,126.3953   $1,126.41   $1,126.40   $1,126.40