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	$247.27	4.608%	$258.6642	$258.66	$258.65	$258.70
Purchase #2	$21.77	7.383%	$23.3773	$23.38	$23.40	$23.40
Purchase #3	$32.59	10.581%	$36.0383	$36.04	$36.05	$36.00
Purchase #4	$238.69	10.846%	$264.5783	$264.58	$264.60	$264.60
Purchase #5	$209.59	4.695%	$219.4303	$219.43	$219.45	$219.40
Purchase #6	$226.76	11.680%	$253.2456	$253.25	$253.25	$253.20
Purchase #7	$84.39	7.383%	$90.6205	$90.62	$90.60	$90.60
7 purchase totals =	$1,061.06		$1,145.9545	$1,145.96	$1,146.00	$1,145.90