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	$173.61	10.519%	$191.872	$191.87	$191.85	$191.90
Purchase #2	$224.92	3.612%	$233.0441	$233.04	$233.05	$233.00
Purchase #3	$158.82	9.451%	$173.8301	$173.83	$173.85	$173.80
Purchase #4	$84.80	7.242%	$90.9412	$90.94	$90.95	$90.90
Purchase #5	$174.44	7.316%	$187.202	$187.20	$187.20	$187.20
Purchase #6	$53.75	8.432%	$58.2822	$58.28	$58.30	$58.30
Purchase #7	$165.33	5.485%	$174.3984	$174.40	$174.40	$174.40
7 purchase totals =	$1,035.67		$1,109.5700	$1,109.56	$1,109.60	$1,109.50