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	$159.89	7.754%	$172.2879	$172.29	$172.30	$172.30
Purchase #2	$234.52	10.740%	$259.7074	$259.71	$259.70	$259.70
Purchase #3	$36.81	9.835%	$40.4303	$40.43	$40.45	$40.40
Purchase #4	$99.83	3.454%	$103.2781	$103.28	$103.30	$103.30
Purchase #5	$67.31	9.216%	$73.5133	$73.51	$73.50	$73.50
Purchase #6	$13.31	3.194%	$13.7351	$13.74	$13.75	$13.70
Purchase #7	$89.93	5.215%	$94.6198	$94.62	$94.60	$94.60
7 purchase totals =	$701.60		$757.5719	$757.58	$757.60	$757.50