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 $104.68   5.335%   $110.2647   $110.26   $110.25   $110.30  
  Purchase #2 $149.35   8.428%   $161.9372   $161.94   $161.95   $161.90  
  Purchase #3 $213.41   7.763%   $229.977   $229.98   $230.00   $230.00  
  Purchase #4 $64.67   3.192%   $66.7343   $66.73   $66.75   $66.70  
  Purchase #5 $42.81   6.838%   $45.7373   $45.74   $45.75   $45.70  
  Purchase #6 $188.42   7.133%   $201.86   $201.86   $201.85   $201.90  
  Purchase #7 $249.70   3.407%   $258.2073   $258.21   $258.20   $258.20  
  7 purchase totals = $1,013.04       $1,074.7178   $1,074.72   $1,074.75   $1,074.70