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	$146.42	9.145%	$159.8101	$159.81	$159.80	$159.80
Purchase #2	$32.72	7.174%	$35.0673	$35.07	$35.05	$35.10
Purchase #3	$96.86	4.135%	$100.8652	$100.87	$100.85	$100.90
Purchase #4	$13.82	5.246%	$14.545	$14.55	$14.55	$14.50
Purchase #5	$219.38	10.464%	$242.3359	$242.34	$242.35	$242.30
Purchase #6	$148.85	12.367%	$167.2583	$167.26	$167.25	$167.30
Purchase #7	$150.73	13.525%	$171.1162	$171.12	$171.10	$171.10
7 purchase totals =	$808.78		$890.9980	$891.02	$890.95	$891.00