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	$167.92	6.312%	$178.5191	$178.52	$178.50	$178.50
Purchase #2	$95.46	5.771%	$100.969	$100.97	$100.95	$101.00
Purchase #3	$60.70	7.845%	$65.4619	$65.46	$65.45	$65.50
Purchase #4	$171.56	7.853%	$185.0326	$185.03	$185.05	$185.00
Purchase #5	$47.37	13.324%	$53.6816	$53.68	$53.70	$53.70
Purchase #6	$175.89	13.191%	$199.0916	$199.09	$199.10	$199.10
Purchase #7	$80.32	10.158%	$88.4789	$88.48	$88.50	$88.50
7 purchase totals =	$799.22		$871.2347	$871.23	$871.25	$871.30