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	$99.68	8.590%	$108.2425	$108.24	$108.25	$108.20
Purchase #2	$108.48	7.499%	$116.6149	$116.61	$116.60	$116.60
Purchase #3	$149.60	5.868%	$158.3785	$158.38	$158.40	$158.40
Purchase #4	$210.59	7.215%	$225.7841	$225.78	$225.80	$225.80
Purchase #5	$164.35	4.321%	$171.4516	$171.45	$171.45	$171.50
Purchase #6	$245.92	8.835%	$267.647	$267.65	$267.65	$267.60
Purchase #7	$243.69	4.849%	$255.5065	$255.51	$255.50	$255.50
7 purchase totals =	$1,222.31		$1,303.6251	$1,303.62	$1,303.65	$1,303.60