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	$201.99	3.763%	$209.5909	$209.59	$209.60	$209.60
Purchase #2	$11.91	4.650%	$12.4638	$12.46	$12.45	$12.50
Purchase #3	$133.39	9.321%	$145.8233	$145.82	$145.80	$145.80
Purchase #4	$71.35	7.746%	$76.8768	$76.88	$76.90	$76.90
Purchase #5	$99.50	12.370%	$111.8082	$111.81	$111.80	$111.80
Purchase #6	$56.87	4.841%	$59.6231	$59.62	$59.60	$59.60
Purchase #7	$172.45	7.718%	$185.7597	$185.76	$185.75	$185.80
7 purchase totals =	$747.46		$801.9458	$801.94	$801.90	$802.00