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	$182.79	4.229%	$190.5202	$190.52	$190.50	$190.50
Purchase #2	$124.76	6.331%	$132.6586	$132.66	$132.65	$132.70
Purchase #3	$155.32	11.658%	$173.4272	$173.43	$173.45	$173.40
Purchase #4	$179.55	9.395%	$196.4187	$196.42	$196.40	$196.40
Purchase #5	$43.87	9.478%	$48.028	$48.03	$48.05	$48.00
Purchase #6	$117.49	3.190%	$121.2379	$121.24	$121.25	$121.20
Purchase #7	$145.96	8.428%	$158.2615	$158.26	$158.25	$158.30
7 purchase totals =	$949.74		$1,020.5521	$1,020.56	$1,020.55	$1,020.50