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 $188.41   7.290%   $202.1451   $202.15   $202.15   $202.10  
  Purchase #2 $60.59   7.530%   $65.1524   $65.15   $65.15   $65.20  
  Purchase #3 $194.61   5.802%   $205.9013   $205.90   $205.90   $205.90  
  Purchase #4 $83.25   12.796%   $93.9027   $93.90   $93.90   $93.90  
  Purchase #5 $92.70   13.791%   $105.4843   $105.48   $105.50   $105.50  
  Purchase #6 $117.41   3.339%   $121.3303   $121.33   $121.35   $121.30  
  Purchase #7 $239.79   3.255%   $247.5952   $247.60   $247.60   $247.60  
  7 purchase totals = $976.76       $1,041.5113   $1,041.51   $1,041.55   $1,041.50