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 $88.32   7.628%   $95.057   $95.06   $95.05   $95.10  
  Purchase #2 $181.96   13.408%   $206.3572   $206.36   $206.35   $206.40  
  Purchase #3 $13.96   3.552%   $14.4559   $14.46   $14.45   $14.50  
  Purchase #4 $211.97   8.528%   $230.0468   $230.05   $230.05   $230.00  
  Purchase #5 $142.54   5.235%   $150.002   $150.00   $150.00   $150.00  
  Purchase #6 $8.41   3.610%   $8.7136   $8.71   $8.70   $8.70  
  Purchase #7 $106.34   6.767%   $113.536   $113.54   $113.55   $113.50  
  7 purchase totals = $753.50       $818.1685   $818.18   $818.15   $818.20