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 $215.95   3.496%   $223.4996   $223.50   $223.50   $223.50  
  Purchase #2 $211.40   7.839%   $227.9716   $227.97   $227.95   $228.00  
  Purchase #3 $238.71   12.519%   $268.5941   $268.59   $268.60   $268.60  
  Purchase #4 $99.63   11.218%   $110.8065   $110.81   $110.80   $110.80  
  Purchase #5 $54.68   4.161%   $56.9552   $56.96   $56.95   $57.00  
  Purchase #6 $161.99   4.700%   $169.6035   $169.60   $169.60   $169.60  
  Purchase #7 $62.62   5.557%   $66.0998   $66.10   $66.10   $66.10  
  7 purchase totals = $1,044.98       $1,123.5303   $1,123.53   $1,123.50   $1,123.60