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	$35.76	4.363%	$37.3202	$37.32	$37.30	$37.30
Purchase #2	$136.81	13.736%	$155.6022	$155.60	$155.60	$155.60
Purchase #3	$106.55	4.555%	$111.4034	$111.40	$111.40	$111.40
Purchase #4	$115.93	10.160%	$127.7085	$127.71	$127.70	$127.70
Purchase #5	$70.37	3.552%	$72.8695	$72.87	$72.85	$72.90
Purchase #6	$74.48	4.206%	$77.6126	$77.61	$77.60	$77.60
Purchase #7	$189.57	5.827%	$200.6162	$200.62	$200.60	$200.60
7 purchase totals =	$729.47		$783.1326	$783.13	$783.05	$783.10