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 $210.65   12.495%   $236.9707   $236.97   $236.95   $237.00  
  Purchase #2 $245.41   3.594%   $254.23   $254.23   $254.25   $254.20  
  Purchase #3 $53.92   7.412%   $57.9166   $57.92   $57.90   $57.90  
  Purchase #4 $62.34   10.171%   $68.6806   $68.68   $68.70   $68.70  
  Purchase #5 $237.69   5.866%   $251.6329   $251.63   $251.65   $251.60  
  Purchase #6 $71.93   12.475%   $80.9033   $80.90   $80.90   $80.90  
  Purchase #7 $129.44   4.658%   $135.4693   $135.47   $135.45   $135.50  
  7 purchase totals = $1,011.38       $1,085.8034   $1,085.80   $1,085.80   $1,085.80