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	$10.76	5.557%	$11.3579	$11.36	$11.35	$11.40
Purchase #2	$41.70	3.784%	$43.2779	$43.28	$43.30	$43.30
Purchase #3	$93.81	3.729%	$97.3082	$97.31	$97.30	$97.30
Purchase #4	$54.53	9.683%	$59.8101	$59.81	$59.80	$59.80
Purchase #5	$111.45	6.548%	$118.7477	$118.75	$118.75	$118.70
Purchase #6	$80.70	10.542%	$89.2074	$89.21	$89.20	$89.20
Purchase #7	$94.45	11.825%	$105.6187	$105.62	$105.60	$105.60
7 purchase totals =	$487.40		$525.3279	$525.34	$525.30	$525.30