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	$74.64	10.481%	$82.463	$82.46	$82.45	$82.50
Purchase #2	$249.40	10.610%	$275.8613	$275.86	$275.85	$275.90
Purchase #3	$67.91	12.817%	$76.614	$76.61	$76.60	$76.60
Purchase #4	$100.50	6.504%	$107.0365	$107.04	$107.05	$107.00
Purchase #5	$153.63	12.264%	$172.4712	$172.47	$172.45	$172.50
Purchase #6	$9.62	6.829%	$10.2769	$10.28	$10.30	$10.30
Purchase #7	$34.69	7.722%	$37.3688	$37.37	$37.35	$37.40
7 purchase totals =	$690.39		$762.0917	$762.09	$762.05	$762.20