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 $239.35   10.550%   $264.6014   $264.60   $264.60   $264.60  
  Purchase #2 $117.89   6.730%   $125.824   $125.82   $125.80   $125.80  
  Purchase #3 $73.78   7.316%   $79.1777   $79.18   $79.20   $79.20  
  Purchase #4 $163.95   13.399%   $185.9177   $185.92   $185.90   $185.90  
  Purchase #5 $212.81   8.847%   $231.6373   $231.64   $231.65   $231.60  
  Purchase #6 $249.91   4.370%   $260.8311   $260.83   $260.85   $260.80  
  Purchase #7 $206.80   6.369%   $219.9711   $219.97   $219.95   $220.00  
  7 purchase totals = $1,264.49       $1,367.9603   $1,367.96   $1,367.95   $1,367.90