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	$127.98	12.246%	$143.6524	$143.65	$143.65	$143.70
Purchase #2	$121.72	13.705%	$138.4017	$138.40	$138.40	$138.40
Purchase #3	$98.34	10.120%	$108.292	$108.29	$108.30	$108.30
Purchase #4	$131.38	11.160%	$146.042	$146.04	$146.05	$146.00
Purchase #5	$18.69	13.810%	$21.2711	$21.27	$21.25	$21.30
Purchase #6	$55.78	7.443%	$59.9317	$59.93	$59.95	$59.90
Purchase #7	$94.45	13.143%	$106.8636	$106.86	$106.85	$106.90
7 purchase totals =	$648.34		$724.4545	$724.44	$724.45	$724.50