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	$243.68	4.538%	$254.7382	$254.74	$254.75	$254.70
Purchase #2	$221.69	11.602%	$247.4105	$247.41	$247.40	$247.40
Purchase #3	$145.80	12.517%	$164.0498	$164.05	$164.05	$164.00
Purchase #4	$53.29	3.538%	$55.1754	$55.18	$55.20	$55.20
Purchase #5	$44.88	12.470%	$50.4765	$50.48	$50.50	$50.50
Purchase #6	$64.37	12.839%	$72.6345	$72.63	$72.65	$72.60
Purchase #7	$145.88	3.555%	$151.066	$151.07	$151.05	$151.10
7 purchase totals =	$919.59		$995.5509	$995.56	$995.60	$995.50