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	$47.38	13.324%	$53.6929	$53.69	$53.70	$53.70
Purchase #2	$82.71	8.329%	$89.5989	$89.60	$89.60	$89.60
Purchase #3	$83.78	10.753%	$92.7889	$92.79	$92.80	$92.80
Purchase #4	$195.93	13.456%	$222.2943	$222.29	$222.30	$222.30
Purchase #5	$141.52	5.734%	$149.6348	$149.63	$149.65	$149.60
Purchase #6	$108.52	4.284%	$113.169	$113.17	$113.15	$113.20
Purchase #7	$172.31	11.158%	$191.5363	$191.54	$191.55	$191.50
7 purchase totals =	$832.15		$912.7151	$912.71	$912.75	$912.70