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 $87.77   5.752%   $92.8185   $92.82   $92.80   $92.80  
  Purchase #2 $195.69   3.435%   $202.412   $202.41   $202.40   $202.40  
  Purchase #3 $130.95   3.838%   $135.9759   $135.98   $136.00   $136.00  
  Purchase #4 $78.51   9.147%   $85.6913   $85.69   $85.70   $85.70  
  Purchase #5 $201.76   6.658%   $215.1932   $215.19   $215.20   $215.20  
  Purchase #6 $154.65   7.715%   $166.5812   $166.58   $166.60   $166.60  
  Purchase #7 $161.33   4.313%   $168.2882   $168.29   $168.30   $168.30  
  7 purchase totals = $1,010.66       $1,066.9603   $1,066.96   $1,067.00   $1,067.00