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	$22.59	13.449%	$25.6281	$25.63	$25.65	$25.60
Purchase #2	$203.37	9.858%	$223.4182	$223.42	$223.40	$223.40
Purchase #3	$45.28	7.868%	$48.8426	$48.84	$48.85	$48.80
Purchase #4	$180.42	3.148%	$186.0996	$186.10	$186.10	$186.10
Purchase #5	$129.71	5.694%	$137.0957	$137.10	$137.10	$137.10
Purchase #6	$32.75	5.244%	$34.4674	$34.47	$34.45	$34.50
Purchase #7	$10.74	9.181%	$11.726	$11.73	$11.75	$11.70
7 purchase totals =	$624.86		$667.2776	$667.29	$667.30	$667.20