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	$48.73	11.458%	$54.3135	$54.31	$54.30	$54.30
Purchase #2	$47.30	12.671%	$53.2934	$53.29	$53.30	$53.30
Purchase #3	$47.69	13.733%	$54.2393	$54.24	$54.25	$54.20
Purchase #4	$44.32	4.671%	$46.3902	$46.39	$46.40	$46.40
Purchase #5	$108.89	12.412%	$122.4054	$122.41	$122.40	$122.40
Purchase #6	$203.56	8.503%	$220.8687	$220.87	$220.85	$220.90
Purchase #7	$58.94	4.383%	$61.5233	$61.52	$61.50	$61.50
7 purchase totals =	$559.43		$613.0338	$613.03	$613.00	$613.00