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	$114.38	11.412%	$127.433	$127.43	$127.45	$127.40
Purchase #2	$61.89	7.359%	$66.4445	$66.44	$66.45	$66.40
Purchase #3	$61.83	12.626%	$69.6367	$69.64	$69.65	$69.60
Purchase #4	$238.77	10.154%	$263.0147	$263.01	$263.00	$263.00
Purchase #5	$49.56	9.643%	$54.3391	$54.34	$54.35	$54.30
Purchase #6	$218.64	11.733%	$244.293	$244.29	$244.30	$244.30
Purchase #7	$23.45	11.662%	$26.1847	$26.18	$26.20	$26.20
7 purchase totals =	$768.52		$851.3457	$851.33	$851.40	$851.20