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 $125.94   4.763%   $131.9385   $131.94   $131.95   $131.90  
  Purchase #2 $192.78   7.690%   $207.6048   $207.60   $207.60   $207.60  
  Purchase #3 $204.77   10.725%   $226.7316   $226.73   $226.75   $226.70  
  Purchase #4 $234.42   8.152%   $253.5299   $253.53   $253.55   $253.50  
  Purchase #5 $248.82   8.852%   $270.8455   $270.85   $270.85   $270.80  
  Purchase #6 $33.67   10.238%   $37.1171   $37.12   $37.10   $37.10  
  Purchase #7 $23.44   7.281%   $25.1467   $25.15   $25.15   $25.10  
  7 purchase totals = $1,063.84       $1,152.9141   $1,152.92   $1,152.95   $1,152.70