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	$130.80	13.240%	$148.1179	$148.12	$148.10	$148.10
Purchase #2	$78.33	4.338%	$81.728	$81.73	$81.75	$81.70
Purchase #3	$150.43	3.245%	$155.3115	$155.31	$155.30	$155.30
Purchase #4	$83.52	6.735%	$89.1451	$89.15	$89.15	$89.10
Purchase #5	$94.32	10.811%	$104.5169	$104.52	$104.50	$104.50
Purchase #6	$111.39	10.205%	$122.7573	$122.76	$122.75	$122.80
Purchase #7	$214.63	3.728%	$222.6314	$222.63	$222.65	$222.60
7 purchase totals =	$863.42		$924.2081	$924.22	$924.20	$924.10