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	$221.36	7.643%	$238.2785	$238.28	$238.30	$238.30
Purchase #2	$93.88	6.797%	$100.261	$100.26	$100.25	$100.30
Purchase #3	$155.74	10.461%	$172.032	$172.03	$172.05	$172.00
Purchase #4	$146.34	13.330%	$165.8471	$165.85	$165.85	$165.80
Purchase #5	$111.68	8.265%	$120.9104	$120.91	$120.90	$120.90
Purchase #6	$192.44	6.527%	$205.0006	$205.00	$205.00	$205.00
Purchase #7	$18.95	7.836%	$20.4349	$20.43	$20.45	$20.40
7 purchase totals =	$940.39		$1,022.7645	$1,022.76	$1,022.80	$1,022.70