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 $83.60   13.604%   $94.9729   $94.97   $94.95   $95.00  
  Purchase #2 $69.82   5.848%   $73.9031   $73.90   $73.90   $73.90  
  Purchase #3 $64.51   5.470%   $68.0387   $68.04   $68.05   $68.00  
  Purchase #4 $22.72   11.743%   $25.388   $25.39   $25.40   $25.40  
  Purchase #5 $186.47   3.297%   $192.6179   $192.62   $192.60   $192.60  
  Purchase #6 $212.79   4.422%   $222.1996   $222.20   $222.20   $222.20  
  Purchase #7 $146.70   6.172%   $155.7543   $155.75   $155.75   $155.80  
  7 purchase totals = $786.61       $832.8745   $832.87   $832.85   $832.90