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	$67.86	8.616%	$73.7068	$73.71	$73.70	$73.70
Purchase #2	$59.53	10.792%	$65.9545	$65.95	$65.95	$66.00
Purchase #3	$248.70	3.233%	$256.7405	$256.74	$256.75	$256.70
Purchase #4	$235.92	8.466%	$255.893	$255.89	$255.90	$255.90
Purchase #5	$216.47	3.217%	$223.4338	$223.43	$223.45	$223.40
Purchase #6	$138.94	10.236%	$153.1619	$153.16	$153.15	$153.20
Purchase #7	$156.53	9.285%	$171.0638	$171.06	$171.05	$171.10
7 purchase totals =	$1,123.95		$1,199.9543	$1,199.94	$1,199.95	$1,200.00