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	$52.73	3.112%	$54.371	$54.37	$54.35	$54.40
Purchase #2	$64.60	10.205%	$71.1924	$71.19	$71.20	$71.20
Purchase #3	$223.39	9.457%	$244.516	$244.52	$244.50	$244.50
Purchase #4	$30.28	11.662%	$33.8113	$33.81	$33.80	$33.80
Purchase #5	$48.88	4.601%	$51.129	$51.13	$51.15	$51.10
Purchase #6	$87.58	8.431%	$94.9639	$94.96	$94.95	$95.00
Purchase #7	$129.48	5.722%	$136.8888	$136.89	$136.90	$136.90
7 purchase totals =	$636.94		$686.8724	$686.87	$686.85	$686.90