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 $224.98   9.231%   $245.7479   $245.75   $245.75   $245.70  
  Purchase #2 $205.25   9.769%   $225.3009   $225.30   $225.30   $225.30  
  Purchase #3 $84.31   6.133%   $89.4807   $89.48   $89.50   $89.50  
  Purchase #4 $31.46   13.576%   $35.731   $35.73   $35.75   $35.70  
  Purchase #5 $231.67   5.769%   $245.035   $245.04   $245.05   $245.00  
  Purchase #6 $101.56   11.485%   $113.2242   $113.22   $113.20   $113.20  
  Purchase #7 $77.67   4.687%   $81.3104   $81.31   $81.30   $81.30  
  7 purchase totals = $956.90       $1,035.8301   $1,035.83   $1,035.85   $1,035.70