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 $58.36   7.517%   $62.7469   $62.75   $62.75   $62.70  
  Purchase #2 $247.87   11.632%   $276.7022   $276.70   $276.70   $276.70  
  Purchase #3 $116.38   4.433%   $121.5391   $121.54   $121.55   $121.50  
  Purchase #4 $247.35   9.766%   $271.5062   $271.51   $271.50   $271.50  
  Purchase #5 $88.68   13.497%   $100.6491   $100.65   $100.65   $100.60  
  Purchase #6 $17.97   5.338%   $18.9292   $18.93   $18.95   $18.90  
  Purchase #7 $250.49   8.721%   $272.3352   $272.34   $272.35   $272.30  
  7 purchase totals = $1,027.10       $1,124.4079   $1,124.42   $1,124.45   $1,124.20