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	$88.38	12.331%	$99.2781	$99.28	$99.30	$99.30
Purchase #2	$148.85	4.472%	$155.5066	$155.51	$155.50	$155.50
Purchase #3	$9.84	6.622%	$10.4916	$10.49	$10.50	$10.50
Purchase #4	$127.52	6.764%	$136.1455	$136.15	$136.15	$136.10
Purchase #5	$242.99	10.557%	$268.6425	$268.64	$268.65	$268.60
Purchase #6	$204.79	9.520%	$224.286	$224.29	$224.30	$224.30
Purchase #7	$120.75	3.749%	$125.2769	$125.28	$125.30	$125.30
7 purchase totals =	$943.12		$1,019.6272	$1,019.64	$1,019.70	$1,019.60