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	$203.27	7.606%	$218.7307	$218.73	$218.75	$218.70
Purchase #2	$235.80	3.738%	$244.6142	$244.61	$244.60	$244.60
Purchase #3	$69.69	11.254%	$77.5329	$77.53	$77.55	$77.50
Purchase #4	$158.27	4.523%	$165.4286	$165.43	$165.45	$165.40
Purchase #5	$19.96	13.306%	$22.6159	$22.62	$22.60	$22.60
Purchase #6	$6.98	4.265%	$7.2777	$7.28	$7.30	$7.30
Purchase #7	$40.31	13.559%	$45.7756	$45.78	$45.80	$45.80
7 purchase totals =	$734.28		$781.9756	$781.98	$782.05	$781.90