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 $187.49   4.513%   $195.9514   $195.95   $195.95   $196.00  
  Purchase #2 $132.46   6.148%   $140.6036   $140.60   $140.60   $140.60  
  Purchase #3 $168.26   5.297%   $177.1727   $177.17   $177.15   $177.20  
  Purchase #4 $126.93   13.311%   $143.8257   $143.83   $143.85   $143.80  
  Purchase #5 $194.39   6.544%   $207.1109   $207.11   $207.10   $207.10  
  Purchase #6 $228.38   7.542%   $245.6044   $245.60   $245.60   $245.60  
  Purchase #7 $68.87   6.232%   $73.162   $73.16   $73.15   $73.20  
  7 purchase totals = $1,106.78       $1,183.4307   $1,183.42   $1,183.40   $1,183.50