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 $81.77   13.191%   $92.5563   $92.56   $92.55   $92.60  
  Purchase #2 $225.65   9.495%   $247.0755   $247.08   $247.10   $247.10  
  Purchase #3 $170.69   8.694%   $185.5298   $185.53   $185.55   $185.50  
  Purchase #4 $98.51   9.135%   $107.5089   $107.51   $107.50   $107.50  
  Purchase #5 $153.91   12.707%   $173.4673   $173.47   $173.45   $173.50  
  Purchase #6 $64.39   6.196%   $68.3796   $68.38   $68.40   $68.40  
  Purchase #7 $133.70   4.332%   $139.4919   $139.49   $139.50   $139.50  
  7 purchase totals = $928.62       $1,014.0093   $1,014.02   $1,014.05   $1,014.10