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 $73.74   3.238%   $76.1277   $76.13   $76.15   $76.10  
  Purchase #2 $199.28   7.487%   $214.2001   $214.20   $214.20   $214.20  
  Purchase #3 $218.65   12.160%   $245.2378   $245.24   $245.25   $245.20  
  Purchase #4 $213.53   4.317%   $222.7481   $222.75   $222.75   $222.70  
  Purchase #5 $91.45   7.135%   $97.975   $97.98   $98.00   $98.00  
  Purchase #6 $96.89   6.381%   $103.0726   $103.07   $103.05   $103.10  
  Purchase #7 $66.90   13.293%   $75.793   $75.79   $75.80   $75.80  
  7 purchase totals = $960.44       $1,035.1543   $1,035.16   $1,035.20   $1,035.10