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 $40.67   11.280%   $45.2576   $45.26   $45.25   $45.30  
  Purchase #2 $239.95   4.759%   $251.3692   $251.37   $251.35   $251.40  
  Purchase #3 $59.46   11.112%   $66.0672   $66.07   $66.05   $66.10  
  Purchase #4 $92.47   3.112%   $95.3477   $95.35   $95.35   $95.30  
  Purchase #5 $199.68   7.113%   $213.8832   $213.88   $213.90   $213.90  
  Purchase #6 $201.43   5.434%   $212.3757   $212.38   $212.40   $212.40  
  Purchase #7 $239.51   11.553%   $267.1806   $267.18   $267.20   $267.20  
  7 purchase totals = $1,073.17       $1,151.4812   $1,151.49   $1,151.50   $1,151.60