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	$149.52	7.114%	$160.1569	$160.16	$160.15	$160.20
Purchase #2	$32.89	9.260%	$35.9356	$35.94	$35.95	$35.90
Purchase #3	$23.78	4.679%	$24.8927	$24.89	$24.90	$24.90
Purchase #4	$103.69	4.633%	$108.494	$108.49	$108.50	$108.50
Purchase #5	$179.75	13.740%	$204.4477	$204.45	$204.45	$204.40
Purchase #6	$88.70	13.769%	$100.9131	$100.91	$100.90	$100.90
Purchase #7	$223.86	9.757%	$245.702	$245.70	$245.70	$245.70
7 purchase totals =	$802.19		$880.5420	$880.54	$880.55	$880.50