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	$172.94	7.296%	$185.5577	$185.56	$185.55	$185.60
Purchase #2	$100.49	13.500%	$114.0562	$114.06	$114.05	$114.10
Purchase #3	$118.59	5.162%	$124.7116	$124.71	$124.70	$124.70
Purchase #4	$235.45	5.343%	$248.0301	$248.03	$248.05	$248.00
Purchase #5	$83.59	7.146%	$89.5633	$89.56	$89.55	$89.60
Purchase #6	$55.81	10.186%	$61.4948	$61.49	$61.50	$61.50
Purchase #7	$221.40	4.319%	$230.9623	$230.96	$230.95	$231.00
7 purchase totals =	$988.27		$1,054.3760	$1,054.37	$1,054.35	$1,054.50