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	$171.87	13.774%	$195.5434	$195.54	$195.55	$195.50
Purchase #2	$173.35	10.495%	$191.5431	$191.54	$191.55	$191.50
Purchase #3	$146.32	7.823%	$157.7666	$157.77	$157.75	$157.80
Purchase #4	$223.70	7.398%	$240.2493	$240.25	$240.25	$240.20
Purchase #5	$201.34	10.735%	$222.9538	$222.95	$222.95	$223.00
Purchase #6	$88.42	13.519%	$100.3735	$100.37	$100.35	$100.40
Purchase #7	$161.82	6.343%	$172.0842	$172.08	$172.10	$172.10
7 purchase totals =	$1,166.82		$1,280.5139	$1,280.50	$1,280.50	$1,280.50