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	$46.28	5.675%	$48.9064	$48.91	$48.90	$48.90
Purchase #2	$52.45	9.355%	$57.3567	$57.36	$57.35	$57.40
Purchase #3	$105.60	8.356%	$114.4239	$114.42	$114.40	$114.40
Purchase #4	$94.43	4.865%	$99.024	$99.02	$99.00	$99.00
Purchase #5	$176.98	4.827%	$185.5228	$185.52	$185.50	$185.50
Purchase #6	$103.82	4.192%	$108.1721	$108.17	$108.15	$108.20
Purchase #7	$231.56	6.103%	$245.6921	$245.69	$245.70	$245.70
7 purchase totals =	$811.12		$859.0980	$859.09	$859.00	$859.10