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 $86.75   8.723%   $94.3172   $94.32   $94.30   $94.30  
  Purchase #2 $155.29   4.789%   $162.7268   $162.73   $162.75   $162.70  
  Purchase #3 $82.87   11.600%   $92.4829   $92.48   $92.50   $92.50  
  Purchase #4 $217.88   4.422%   $227.5147   $227.51   $227.50   $227.50  
  Purchase #5 $207.88   9.224%   $227.0549   $227.05   $227.05   $227.10  
  Purchase #6 $95.86   3.640%   $99.3493   $99.35   $99.35   $99.30  
  Purchase #7 $180.77   11.607%   $201.752   $201.75   $201.75   $201.80  
  7 purchase totals = $1,027.30       $1,105.1978   $1,105.19   $1,105.20   $1,105.20