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	$175.30	12.302%	$196.8654	$196.87	$196.85	$196.90
Purchase #2	$35.42	4.346%	$36.9594	$36.96	$36.95	$37.00
Purchase #3	$51.25	7.686%	$55.1891	$55.19	$55.20	$55.20
Purchase #4	$116.68	9.182%	$127.3936	$127.39	$127.40	$127.40
Purchase #5	$18.28	4.239%	$19.0549	$19.05	$19.05	$19.10
Purchase #6	$45.70	8.661%	$49.6581	$49.66	$49.65	$49.70
Purchase #7	$196.39	12.233%	$220.4144	$220.41	$220.40	$220.40
7 purchase totals =	$639.02		$705.5349	$705.53	$705.50	$705.70