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	$67.72	5.242%	$71.2699	$71.27	$71.25	$71.30
Purchase #2	$116.63	5.375%	$122.8989	$122.90	$122.90	$122.90
Purchase #3	$152.43	4.236%	$158.8869	$158.89	$158.90	$158.90
Purchase #4	$128.49	13.759%	$146.1689	$146.17	$146.15	$146.20
Purchase #5	$122.65	13.450%	$139.1464	$139.15	$139.15	$139.10
Purchase #6	$150.38	6.657%	$160.3908	$160.39	$160.40	$160.40
Purchase #7	$18.35	5.367%	$19.3348	$19.33	$19.35	$19.30
7 purchase totals =	$756.65		$818.0966	$818.10	$818.10	$818.10