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 $67.95   11.796%   $75.9654   $75.97   $75.95   $76.00  
  Purchase #2 $16.41   10.827%   $18.1867   $18.19   $18.20   $18.20  
  Purchase #3 $170.26   9.498%   $186.4313   $186.43   $186.45   $186.40  
  Purchase #4 $191.47   7.821%   $206.4449   $206.44   $206.45   $206.40  
  Purchase #5 $244.99   9.762%   $268.9059   $268.91   $268.90   $268.90  
  Purchase #6 $158.30   7.810%   $170.6632   $170.66   $170.65   $170.70  
  Purchase #7 $198.98   5.219%   $209.3648   $209.36   $209.35   $209.40  
  7 purchase totals = $1,048.36       $1,135.9622   $1,135.96   $1,135.95   $1,136.00