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 $59.31   5.501%   $62.5726   $62.57   $62.55   $62.60  
  Purchase #2 $187.98   3.614%   $194.7736   $194.77   $194.75   $194.80  
  Purchase #3 $195.99   7.343%   $210.3815   $210.38   $210.40   $210.40  
  Purchase #4 $153.86   7.524%   $165.4364   $165.44   $165.45   $165.40  
  Purchase #5 $216.26   4.126%   $225.1829   $225.18   $225.20   $225.20  
  Purchase #6 $67.25   9.274%   $73.4868   $73.49   $73.50   $73.50  
  Purchase #7 $102.81   7.621%   $110.6452   $110.65   $110.65   $110.60  
  7 purchase totals = $983.46       $1,042.4790   $1,042.48   $1,042.50   $1,042.50