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 $181.95   7.532%   $195.6545   $195.65   $195.65   $195.70  
  Purchase #2 $83.77   5.253%   $88.1704   $88.17   $88.15   $88.20  
  Purchase #3 $235.60   11.293%   $262.2063   $262.21   $262.20   $262.20  
  Purchase #4 $32.31   8.198%   $34.9588   $34.96   $34.95   $35.00  
  Purchase #5 $104.98   6.402%   $111.7008   $111.70   $111.70   $111.70  
  Purchase #6 $33.76   10.283%   $37.2315   $37.23   $37.25   $37.20  
  Purchase #7 $85.30   8.339%   $92.4132   $92.41   $92.40   $92.40  
  7 purchase totals = $757.67       $822.3355   $822.33   $822.30   $822.40