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 $173.91   11.556%   $194.007   $194.01   $194.00   $194.00  
  Purchase #2 $99.86   12.120%   $111.963   $111.96   $111.95   $112.00  
  Purchase #3 $247.86   5.308%   $261.0164   $261.02   $261.00   $261.00  
  Purchase #4 $199.72   5.444%   $210.5928   $210.59   $210.60   $210.60  
  Purchase #5 $182.46   7.431%   $196.0186   $196.02   $196.00   $196.00  
  Purchase #6 $205.68   12.355%   $231.0918   $231.09   $231.10   $231.10  
  Purchase #7 $63.50   10.364%   $70.0811   $70.08   $70.10   $70.10  
  7 purchase totals = $1,172.99       $1,274.7707   $1,274.77   $1,274.75   $1,274.80