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 $195.46   7.199%   $209.5312   $209.53   $209.55   $209.50  
  Purchase #2 $65.79   4.873%   $68.9959   $69.00   $69.00   $69.00  
  Purchase #3 $158.61   10.504%   $175.2704   $175.27   $175.25   $175.30  
  Purchase #4 $187.42   11.254%   $208.5122   $208.51   $208.50   $208.50  
  Purchase #5 $180.42   10.315%   $199.0303   $199.03   $199.05   $199.00  
  Purchase #6 $191.30   13.437%   $217.005   $217.01   $217.00   $217.00  
  Purchase #7 $16.31   7.696%   $17.5652   $17.57   $17.55   $17.60  
  7 purchase totals = $995.31       $1,095.9102   $1,095.92   $1,095.90   $1,095.90