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 $119.31   6.111%   $126.601   $126.60   $126.60   $126.60  
  Purchase #2 $149.38   7.302%   $160.2877   $160.29   $160.30   $160.30  
  Purchase #3 $14.42   11.416%   $16.0662   $16.07   $16.05   $16.10  
  Purchase #4 $66.86   10.776%   $74.0648   $74.06   $74.05   $74.10  
  Purchase #5 $33.89   9.191%   $37.0048   $37.00   $37.00   $37.00  
  Purchase #6 $158.86   8.246%   $171.9596   $171.96   $171.95   $172.00  
  Purchase #7 $163.31   13.643%   $185.5904   $185.59   $185.60   $185.60  
  7 purchase totals = $706.03       $771.5745   $771.57   $771.55   $771.70