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	$147.74	7.247%	$158.4467	$158.45	$158.45	$158.40
Purchase #2	$60.31	3.317%	$62.3105	$62.31	$62.30	$62.30
Purchase #3	$91.46	9.500%	$100.1487	$100.15	$100.15	$100.10
Purchase #4	$38.59	5.199%	$40.5963	$40.60	$40.60	$40.60
Purchase #5	$89.69	13.394%	$101.7031	$101.70	$101.70	$101.70
Purchase #6	$114.77	13.438%	$130.1928	$130.19	$130.20	$130.20
Purchase #7	$95.86	9.309%	$104.7836	$104.78	$104.80	$104.80
7 purchase totals =	$638.42		$698.1817	$698.18	$698.20	$698.10