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 $43.64   6.193%   $46.3426   $46.34   $46.35   $46.30  
  Purchase #2 $129.86   5.692%   $137.2516   $137.25   $137.25   $137.30  
  Purchase #3 $191.97   5.754%   $203.016   $203.02   $203.00   $203.00  
  Purchase #4 $162.27   13.144%   $183.5988   $183.60   $183.60   $183.60  
  Purchase #5 $75.28   5.547%   $79.4558   $79.46   $79.45   $79.50  
  Purchase #6 $230.28   3.586%   $238.5378   $238.54   $238.55   $238.50  
  Purchase #7 $194.85   11.531%   $217.3182   $217.32   $217.30   $217.30  
  7 purchase totals = $1,028.15       $1,105.5208   $1,105.53   $1,105.50   $1,105.50