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 $117.68   13.745%   $133.8551   $133.86   $133.85   $133.90  
  Purchase #2 $175.96   10.421%   $194.2968   $194.30   $194.30   $194.30  
  Purchase #3 $60.28   7.743%   $64.9475   $64.95   $64.95   $64.90  
  Purchase #4 $185.83   12.687%   $209.4063   $209.41   $209.40   $209.40  
  Purchase #5 $233.71   5.728%   $247.0969   $247.10   $247.10   $247.10  
  Purchase #6 $153.65   9.757%   $168.6416   $168.64   $168.65   $168.60  
  Purchase #7 $166.54   12.137%   $186.753   $186.75   $186.75   $186.80  
  7 purchase totals = $1,093.65       $1,204.9972   $1,205.01   $1,205.00   $1,205.00