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	$183.47	5.638%	$193.814	$193.81	$193.80	$193.80
Purchase #2	$204.35	9.510%	$223.7837	$223.78	$223.80	$223.80
Purchase #3	$156.36	13.139%	$176.9041	$176.90	$176.90	$176.90
Purchase #4	$157.52	7.422%	$169.2111	$169.21	$169.20	$169.20
Purchase #5	$57.49	3.537%	$59.5234	$59.52	$59.50	$59.50
Purchase #6	$107.93	3.123%	$111.3007	$111.30	$111.30	$111.30
Purchase #7	$151.43	7.487%	$162.7676	$162.77	$162.75	$162.80
7 purchase totals =	$1,018.55		$1,097.3046	$1,097.29	$1,097.25	$1,097.30