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 $172.54   13.129%   $195.1928   $195.19   $195.20   $195.20  
  Purchase #2 $92.36   3.213%   $95.3275   $95.33   $95.35   $95.30  
  Purchase #3 $15.27   10.154%   $16.8205   $16.82   $16.80   $16.80  
  Purchase #4 $112.40   3.743%   $116.6071   $116.61   $116.60   $116.60  
  Purchase #5 $194.34   5.593%   $205.2094   $205.21   $205.20   $205.20  
  Purchase #6 $8.83   3.619%   $9.1496   $9.15   $9.15   $9.10  
  Purchase #7 $177.31   11.684%   $198.0269   $198.03   $198.05   $198.00  
  7 purchase totals = $773.05       $836.3338   $836.34   $836.35   $836.20