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	$43.85	10.652%	$48.5209	$48.52	$48.50	$48.50
Purchase #2	$70.62	10.830%	$78.2681	$78.27	$78.25	$78.30
Purchase #3	$25.98	10.612%	$28.737	$28.74	$28.75	$28.70
Purchase #4	$95.56	10.602%	$105.6913	$105.69	$105.70	$105.70
Purchase #5	$107.87	10.592%	$119.2956	$119.30	$119.30	$119.30
Purchase #6	$161.88	4.823%	$169.6875	$169.69	$169.70	$169.70
Purchase #7	$30.76	8.540%	$33.3869	$33.39	$33.40	$33.40
7 purchase totals =	$536.52		$583.5873	$583.60	$583.60	$583.60