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 $104.53   8.718%   $113.6429   $113.64   $113.65   $113.60  
  Purchase #2 $176.49   10.263%   $194.6032   $194.60   $194.60   $194.60  
  Purchase #3 $112.99   5.285%   $118.9615   $118.96   $118.95   $119.00  
  Purchase #4 $147.26   5.121%   $154.8012   $154.80   $154.80   $154.80  
  Purchase #5 $76.83   4.569%   $80.3404   $80.34   $80.35   $80.30  
  Purchase #6 $178.98   13.782%   $203.647   $203.65   $203.65   $203.60  
  Purchase #7 $55.57   4.686%   $58.174   $58.17   $58.15   $58.20  
  7 purchase totals = $852.65       $924.1702   $924.16   $924.15   $924.10