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	$232.25	9.483%	$254.2743	$254.27	$254.25	$254.30
Purchase #2	$221.84	3.727%	$230.108	$230.11	$230.10	$230.10
Purchase #3	$167.83	10.662%	$185.724	$185.72	$185.70	$185.70
Purchase #4	$208.93	6.805%	$223.1477	$223.15	$223.15	$223.10
Purchase #5	$79.37	4.644%	$83.0559	$83.06	$83.05	$83.10
Purchase #6	$33.94	11.435%	$37.821	$37.82	$37.80	$37.80
Purchase #7	$222.62	3.489%	$230.3872	$230.39	$230.40	$230.40
7 purchase totals =	$1,166.78		$1,244.5181	$1,244.52	$1,244.45	$1,244.50