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	$60.28	11.739%	$67.3563	$67.36	$67.35	$67.40
Purchase #2	$233.87	9.236%	$255.4702	$255.47	$255.45	$255.50
Purchase #3	$48.33	5.158%	$50.8229	$50.82	$50.80	$50.80
Purchase #4	$183.37	3.262%	$189.3515	$189.35	$189.35	$189.40
Purchase #5	$242.90	12.866%	$274.1515	$274.15	$274.15	$274.20
Purchase #6	$84.77	11.243%	$94.3007	$94.30	$94.30	$94.30
Purchase #7	$146.39	13.287%	$165.8408	$165.84	$165.85	$165.80
7 purchase totals =	$999.91		$1,097.2939	$1,097.29	$1,097.25	$1,097.40