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	$111.39	5.370%	$117.3716	$117.37	$117.35	$117.40
Purchase #2	$85.53	4.593%	$89.4584	$89.46	$89.45	$89.50
Purchase #3	$95.83	3.568%	$99.2492	$99.25	$99.25	$99.20
Purchase #4	$16.74	6.278%	$17.7909	$17.79	$17.80	$17.80
Purchase #5	$33.64	6.551%	$35.8438	$35.84	$35.85	$35.80
Purchase #6	$56.50	7.470%	$60.7206	$60.72	$60.70	$60.70
Purchase #7	$55.77	5.238%	$58.6912	$58.69	$58.70	$58.70
7 purchase totals =	$455.40		$479.1257	$479.12	$479.10	$479.10