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	$154.34	10.111%	$169.9453	$169.95	$169.95	$169.90
Purchase #2	$140.87	12.527%	$158.5168	$158.52	$158.50	$158.50
Purchase #3	$147.37	12.219%	$165.3771	$165.38	$165.40	$165.40
Purchase #4	$145.93	13.462%	$165.5751	$165.58	$165.60	$165.60
Purchase #5	$5.91	13.449%	$6.7048	$6.70	$6.70	$6.70
Purchase #6	$85.72	12.810%	$96.7007	$96.70	$96.70	$96.70
Purchase #7	$99.93	5.391%	$105.3172	$105.32	$105.30	$105.30
7 purchase totals =	$780.07		$868.1370	$868.15	$868.15	$868.10