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 $49.34   5.318%   $51.9639   $51.96   $51.95   $52.00  
  Purchase #2 $226.42   3.497%   $234.3379   $234.34   $234.35   $234.30  
  Purchase #3 $95.59   4.694%   $100.077   $100.08   $100.10   $100.10  
  Purchase #4 $222.56   8.838%   $242.2299   $242.23   $242.25   $242.20  
  Purchase #5 $196.28   9.707%   $215.3329   $215.33   $215.35   $215.30  
  Purchase #6 $156.37   11.149%   $173.8037   $173.80   $173.80   $173.80  
  Purchase #7 $80.63   8.137%   $87.1909   $87.19   $87.20   $87.20  
  7 purchase totals = $1,027.19       $1,104.9362   $1,104.93   $1,105.00   $1,104.90