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 $204.84   5.555%   $216.2189   $216.22   $216.20   $216.20  
  Purchase #2 $153.41   4.160%   $159.7919   $159.79   $159.80   $159.80  
  Purchase #3 $72.64   3.453%   $75.1483   $75.15   $75.15   $75.10  
  Purchase #4 $202.62   7.195%   $217.1985   $217.20   $217.20   $217.20  
  Purchase #5 $216.48   5.846%   $229.1354   $229.14   $229.15   $229.10  
  Purchase #6 $182.91   10.856%   $202.7667   $202.77   $202.75   $202.80  
  Purchase #7 $60.92   10.470%   $67.2983   $67.30   $67.30   $67.30  
  7 purchase totals = $1,093.82       $1,167.5580   $1,167.57   $1,167.55   $1,167.50