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	$105.60	4.274%	$110.1133	$110.11	$110.10	$110.10
Purchase #2	$165.37	5.146%	$173.8799	$173.88	$173.90	$173.90
Purchase #3	$78.75	10.461%	$86.988	$86.99	$87.00	$87.00
Purchase #4	$139.75	12.223%	$156.8316	$156.83	$156.85	$156.80
Purchase #5	$32.33	13.256%	$36.6157	$36.62	$36.60	$36.60
Purchase #6	$231.44	3.155%	$238.7419	$238.74	$238.75	$238.70
Purchase #7	$144.62	10.162%	$159.3163	$159.32	$159.30	$159.30
7 purchase totals =	$897.86		$962.4867	$962.49	$962.50	$962.40