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	$117.48	12.252%	$131.8736	$131.87	$131.85	$131.90
Purchase #2	$37.66	11.734%	$42.079	$42.08	$42.10	$42.10
Purchase #3	$88.35	4.455%	$92.286	$92.29	$92.30	$92.30
Purchase #4	$242.92	9.618%	$266.284	$266.28	$266.30	$266.30
Purchase #5	$157.99	4.508%	$165.1122	$165.11	$165.10	$165.10
Purchase #6	$250.81	13.250%	$284.0423	$284.04	$284.05	$284.00
Purchase #7	$98.46	13.422%	$111.6753	$111.68	$111.70	$111.70
7 purchase totals =	$993.67		$1,093.3524	$1,093.35	$1,093.40	$1,093.40