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 $212.70   5.157%   $223.6689   $223.67   $223.65   $223.70  
  Purchase #2 $33.35   4.136%   $34.7294   $34.73   $34.75   $34.70  
  Purchase #3 $12.75   9.254%   $13.9299   $13.93   $13.95   $13.90  
  Purchase #4 $47.97   13.155%   $54.2805   $54.28   $54.30   $54.30  
  Purchase #5 $101.36   9.165%   $110.6496   $110.65   $110.65   $110.60  
  Purchase #6 $187.66   11.858%   $209.9127   $209.91   $209.90   $209.90  
  Purchase #7 $217.66   9.278%   $237.8545   $237.85   $237.85   $237.90  
  7 purchase totals = $813.45       $885.0255   $885.02   $885.05   $885.00