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 $119.30   5.712%   $126.1144   $126.11   $126.10   $126.10  
  Purchase #2 $209.30   12.352%   $235.1527   $235.15   $235.15   $235.20  
  Purchase #3 $185.33   5.553%   $195.6214   $195.62   $195.60   $195.60  
  Purchase #4 $127.88   13.827%   $145.562   $145.56   $145.55   $145.60  
  Purchase #5 $93.29   10.174%   $102.7813   $102.78   $102.80   $102.80  
  Purchase #6 $127.92   4.722%   $133.9604   $133.96   $133.95   $134.00  
  Purchase #7 $64.75   10.613%   $71.6219   $71.62   $71.60   $71.60  
  7 purchase totals = $927.77       $1,010.8141   $1,010.80   $1,010.75   $1,010.90