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	$214.64	3.450%	$222.0451	$222.05	$222.05	$222.00
Purchase #2	$131.76	13.457%	$149.4909	$149.49	$149.50	$149.50
Purchase #3	$79.40	13.691%	$90.2707	$90.27	$90.25	$90.30
Purchase #4	$141.74	4.250%	$147.764	$147.76	$147.75	$147.80
Purchase #5	$78.68	8.486%	$85.3568	$85.36	$85.35	$85.40
Purchase #6	$58.40	5.517%	$61.6219	$61.62	$61.60	$61.60
Purchase #7	$223.45	6.565%	$238.1195	$238.12	$238.10	$238.10
7 purchase totals =	$928.07		$994.6689	$994.67	$994.60	$994.70