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	$47.47	6.288%	$50.4549	$50.45	$50.45	$50.50
Purchase #2	$239.77	13.120%	$271.2278	$271.23	$271.25	$271.20
Purchase #3	$133.49	10.615%	$147.66	$147.66	$147.65	$147.70
Purchase #4	$49.52	7.622%	$53.2944	$53.29	$53.30	$53.30
Purchase #5	$92.92	13.511%	$105.4744	$105.47	$105.45	$105.50
Purchase #6	$248.98	9.820%	$273.4298	$273.43	$273.45	$273.40
Purchase #7	$159.26	5.613%	$168.1993	$168.20	$168.20	$168.20
7 purchase totals =	$971.41		$1,069.7406	$1,069.73	$1,069.75	$1,069.80