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	$205.75	6.197%	$218.5003	$218.50	$218.50	$218.50
Purchase #2	$176.61	4.749%	$184.9972	$185.00	$185.00	$185.00
Purchase #3	$130.63	6.830%	$139.552	$139.55	$139.55	$139.60
Purchase #4	$107.82	3.532%	$111.6282	$111.63	$111.65	$111.60
Purchase #5	$129.26	3.869%	$134.2611	$134.26	$134.25	$134.30
Purchase #6	$46.76	3.723%	$48.5009	$48.50	$48.50	$48.50
Purchase #7	$215.33	6.386%	$229.081	$229.08	$229.10	$229.10
7 purchase totals =	$1,012.16		$1,066.5207	$1,066.52	$1,066.55	$1,066.60