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	$231.87	5.431%	$244.4629	$244.46	$244.45	$244.50
Purchase #2	$169.87	10.424%	$187.5772	$187.58	$187.60	$187.60
Purchase #3	$137.38	4.793%	$143.9646	$143.96	$143.95	$144.00
Purchase #4	$37.58	13.137%	$42.5169	$42.52	$42.50	$42.50
Purchase #5	$129.81	12.833%	$146.4685	$146.47	$146.45	$146.50
Purchase #6	$187.34	13.294%	$212.245	$212.25	$212.25	$212.20
Purchase #7	$91.81	11.482%	$102.3516	$102.35	$102.35	$102.40
7 purchase totals =	$985.66		$1,079.5867	$1,079.59	$1,079.55	$1,079.70