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	$48.57	10.160%	$53.5047	$53.50	$53.50	$53.50
Purchase #2	$60.96	4.106%	$63.463	$63.46	$63.45	$63.50
Purchase #3	$10.67	4.874%	$11.1901	$11.19	$11.20	$11.20
Purchase #4	$91.37	12.310%	$102.6176	$102.62	$102.60	$102.60
Purchase #5	$83.94	10.139%	$92.4507	$92.45	$92.45	$92.50
Purchase #6	$241.75	4.836%	$253.441	$253.44	$253.45	$253.40
Purchase #7	$229.67	11.720%	$256.5873	$256.59	$256.60	$256.60
7 purchase totals =	$766.93		$833.2544	$833.25	$833.25	$833.30