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	$92.67	9.286%	$101.2753	$101.28	$101.30	$101.30
Purchase #2	$74.40	13.859%	$84.7111	$84.71	$84.70	$84.70
Purchase #3	$99.46	7.173%	$106.5943	$106.59	$106.60	$106.60
Purchase #4	$242.86	10.831%	$269.1642	$269.16	$269.15	$269.20
Purchase #5	$51.43	4.782%	$53.8894	$53.89	$53.90	$53.90
Purchase #6	$50.38	7.444%	$54.1303	$54.13	$54.15	$54.10
Purchase #7	$196.33	4.603%	$205.3671	$205.37	$205.35	$205.40
7 purchase totals =	$807.53		$875.1317	$875.13	$875.15	$875.20