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 $214.59   9.185%   $234.3001   $234.30   $234.30   $234.30  
  Purchase #2 $30.46   10.338%   $33.609   $33.61   $33.60   $33.60  
  Purchase #3 $10.29   10.327%   $11.3526   $11.35   $11.35   $11.40  
  Purchase #4 $215.85   10.436%   $238.3761   $238.38   $238.40   $238.40  
  Purchase #5 $118.69   9.664%   $130.1602   $130.16   $130.15   $130.20  
  Purchase #6 $195.96   7.161%   $209.9927   $209.99   $210.00   $210.00  
  Purchase #7 $176.59   6.496%   $188.0613   $188.06   $188.05   $188.10  
  7 purchase totals = $962.43       $1,045.8520   $1,045.85   $1,045.85   $1,046.00