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 $44.74   4.554%   $46.7775   $46.78   $46.80   $46.80  
  Purchase #2 $95.26   13.482%   $108.103   $108.10   $108.10   $108.10  
  Purchase #3 $133.31   13.390%   $151.1602   $151.16   $151.15   $151.20  
  Purchase #4 $113.28   11.813%   $126.6618   $126.66   $126.65   $126.70  
  Purchase #5 $237.59   12.628%   $267.5929   $267.59   $267.60   $267.60  
  Purchase #6 $57.90   11.487%   $64.551   $64.55   $64.55   $64.60  
  Purchase #7 $213.45   13.856%   $243.0256   $243.03   $243.05   $243.00  
  7 purchase totals = $895.53       $1,007.8720   $1,007.87   $1,007.90   $1,008.00