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 $44.93   8.230%   $48.6277   $48.63   $48.65   $48.60  
  Purchase #2 $15.91   12.262%   $17.8609   $17.86   $17.85   $17.90  
  Purchase #3 $53.97   12.642%   $60.7929   $60.79   $60.80   $60.80  
  Purchase #4 $217.32   7.473%   $233.5603   $233.56   $233.55   $233.60  
  Purchase #5 $194.39   6.304%   $206.6443   $206.64   $206.65   $206.60  
  Purchase #6 $226.55   7.755%   $244.119   $244.12   $244.10   $244.10  
  Purchase #7 $240.25   6.701%   $256.3492   $256.35   $256.35   $256.30  
  7 purchase totals = $993.32       $1,067.9543   $1,067.95   $1,067.95   $1,067.90