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	$55.77	8.250%	$60.371	$60.37	$60.35	$60.40
Purchase #2	$187.69	13.628%	$213.2684	$213.27	$213.25	$213.30
Purchase #3	$101.61	8.129%	$109.8699	$109.87	$109.85	$109.90
Purchase #4	$43.73	11.817%	$48.8976	$48.90	$48.90	$48.90
Purchase #5	$167.94	10.498%	$185.5703	$185.57	$185.55	$185.60
Purchase #6	$32.52	5.347%	$34.2588	$34.26	$34.25	$34.30
Purchase #7	$103.49	6.215%	$109.9219	$109.92	$109.90	$109.90
7 purchase totals =	$692.75		$762.1579	$762.16	$762.05	$762.30