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 $94.78   3.532%   $98.1276   $98.13   $98.15   $98.10  
  Purchase #2 $236.42   13.184%   $267.5896   $267.59   $267.60   $267.60  
  Purchase #3 $166.87   10.646%   $184.635   $184.64   $184.65   $184.60  
  Purchase #4 $20.55   12.540%   $23.127   $23.13   $23.15   $23.10  
  Purchase #5 $142.43   6.631%   $151.8745   $151.87   $151.85   $151.90  
  Purchase #6 $21.28   4.417%   $22.2199   $22.22   $22.20   $22.20  
  Purchase #7 $245.58   8.670%   $266.8718   $266.87   $266.85   $266.90  
  7 purchase totals = $927.91       $1,014.4454   $1,014.45   $1,014.45   $1,014.40