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	$132.81	7.238%	$142.4228	$142.42	$142.40	$142.40
Purchase #2	$158.97	4.268%	$165.7548	$165.75	$165.75	$165.80
Purchase #3	$78.51	13.474%	$89.0884	$89.09	$89.10	$89.10
Purchase #4	$17.54	7.463%	$18.849	$18.85	$18.85	$18.80
Purchase #5	$189.67	13.732%	$215.7155	$215.72	$215.70	$215.70
Purchase #6	$27.65	5.447%	$29.1561	$29.16	$29.15	$29.20
Purchase #7	$19.91	12.424%	$22.3836	$22.38	$22.40	$22.40
7 purchase totals =	$625.06		$683.3702	$683.37	$683.35	$683.40