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	$123.53	3.265%	$127.5633	$127.56	$127.55	$127.60
Purchase #2	$195.75	10.733%	$216.7598	$216.76	$216.75	$216.80
Purchase #3	$30.68	8.630%	$33.3277	$33.33	$33.35	$33.30
Purchase #4	$93.51	6.762%	$99.8331	$99.83	$99.85	$99.80
Purchase #5	$159.59	11.829%	$178.4679	$178.47	$178.45	$178.50
Purchase #6	$13.97	3.244%	$14.4232	$14.42	$14.40	$14.40
Purchase #7	$71.67	7.828%	$77.2803	$77.28	$77.30	$77.30
7 purchase totals =	$688.70		$747.6553	$747.65	$747.65	$747.70