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	$102.78	7.391%	$110.3765	$110.38	$110.40	$110.40
Purchase #2	$165.30	6.639%	$176.2743	$176.27	$176.25	$176.30
Purchase #3	$118.38	7.434%	$127.1804	$127.18	$127.20	$127.20
Purchase #4	$144.49	7.820%	$155.7891	$155.79	$155.80	$155.80
Purchase #5	$19.89	10.512%	$21.9808	$21.98	$22.00	$22.00
Purchase #6	$178.51	11.736%	$199.4599	$199.46	$199.45	$199.50
Purchase #7	$72.41	8.109%	$78.2817	$78.28	$78.30	$78.30
7 purchase totals =	$801.76		$869.3427	$869.34	$869.40	$869.50