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	$231.59	11.588%	$258.4266	$258.43	$258.45	$258.40
Purchase #2	$54.53	8.609%	$59.2245	$59.22	$59.20	$59.20
Purchase #3	$108.59	3.158%	$112.0193	$112.02	$112.00	$112.00
Purchase #4	$142.60	8.777%	$155.116	$155.12	$155.10	$155.10
Purchase #5	$186.25	11.529%	$207.7228	$207.72	$207.70	$207.70
Purchase #6	$195.89	11.430%	$218.2802	$218.28	$218.30	$218.30
Purchase #7	$91.62	13.208%	$103.7212	$103.72	$103.70	$103.70
7 purchase totals =	$1,011.07		$1,114.5106	$1,114.51	$1,114.45	$1,114.40