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 $182.80   6.771%   $195.1774   $195.18   $195.20   $195.20  
  Purchase #2 $142.67   12.237%   $160.1285   $160.13   $160.15   $160.10  
  Purchase #3 $209.53   3.373%   $216.5974   $216.60   $216.60   $216.60  
  Purchase #4 $230.40   11.181%   $256.161   $256.16   $256.15   $256.20  
  Purchase #5 $24.60   8.126%   $26.599   $26.60   $26.60   $26.60  
  Purchase #6 $51.81   13.717%   $58.9168   $58.92   $58.90   $58.90  
  Purchase #7 $226.29   4.360%   $236.1562   $236.16   $236.15   $236.20  
  7 purchase totals = $1,068.10       $1,149.7363   $1,149.75   $1,149.75   $1,149.80