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 $67.28   9.592%   $73.7335   $73.73   $73.75   $73.70  
  Purchase #2 $98.32   11.121%   $109.2542   $109.25   $109.25   $109.30  
  Purchase #3 $182.79   10.516%   $202.0122   $202.01   $202.00   $202.00  
  Purchase #4 $193.27   10.550%   $213.66   $213.66   $213.65   $213.70  
  Purchase #5 $142.53   6.321%   $151.5393   $151.54   $151.55   $151.50  
  Purchase #6 $173.45   8.306%   $187.8568   $187.86   $187.85   $187.90  
  Purchase #7 $166.67   3.583%   $172.6418   $172.64   $172.65   $172.60  
  7 purchase totals = $1,024.31       $1,110.6978   $1,110.69   $1,110.70   $1,110.70