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 $71.28   3.363%   $73.6771   $73.68   $73.70   $73.70  
  Purchase #2 $59.53   4.804%   $62.3898   $62.39   $62.40   $62.40  
  Purchase #3 $71.71   4.222%   $74.7376   $74.74   $74.75   $74.70  
  Purchase #4 $148.61   9.445%   $162.6462   $162.65   $162.65   $162.60  
  Purchase #5 $242.85   13.376%   $275.3336   $275.33   $275.35   $275.30  
  Purchase #6 $98.30   9.388%   $107.5284   $107.53   $107.55   $107.50  
  Purchase #7 $120.81   3.675%   $125.2498   $125.25   $125.25   $125.20  
  7 purchase totals = $813.09       $881.5625   $881.57   $881.65   $881.40