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 $219.86   11.225%   $244.5393   $244.54   $244.55   $244.50  
  Purchase #2 $98.98   5.532%   $104.4556   $104.46   $104.45   $104.50  
  Purchase #3 $228.90   9.297%   $250.1808   $250.18   $250.20   $250.20  
  Purchase #4 $23.91   5.584%   $25.2451   $25.25   $25.25   $25.20  
  Purchase #5 $119.59   8.253%   $129.4598   $129.46   $129.45   $129.50  
  Purchase #6 $53.28   10.541%   $58.8962   $58.90   $58.90   $58.90  
  Purchase #7 $56.47   10.773%   $62.5535   $62.55   $62.55   $62.60  
  7 purchase totals = $800.99       $875.3303   $875.34   $875.35   $875.40