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 $86.62   8.514%   $93.9948   $93.99   $94.00   $94.00  
  Purchase #2 $110.40   9.648%   $121.0514   $121.05   $121.05   $121.10  
  Purchase #3 $32.86   4.145%   $34.222   $34.22   $34.20   $34.20  
  Purchase #4 $7.55   6.113%   $8.0115   $8.01   $8.00   $8.00  
  Purchase #5 $8.66   6.130%   $9.1909   $9.19   $9.20   $9.20  
  Purchase #6 $249.74   8.351%   $270.5958   $270.60   $270.60   $270.60  
  Purchase #7 $69.74   10.761%   $77.2447   $77.24   $77.25   $77.20  
  7 purchase totals = $565.57       $614.3111   $614.30   $614.30   $614.30