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	$46.40	4.605%	$48.5367	$48.54	$48.55	$48.50
Purchase #2	$139.72	3.255%	$144.2679	$144.27	$144.25	$144.30
Purchase #3	$35.55	11.723%	$39.7175	$39.72	$39.70	$39.70
Purchase #4	$121.55	7.207%	$130.3101	$130.31	$130.30	$130.30
Purchase #5	$243.69	11.839%	$272.5405	$272.54	$272.55	$272.50
Purchase #6	$49.30	11.653%	$55.0449	$55.04	$55.05	$55.00
Purchase #7	$115.62	10.126%	$127.3277	$127.33	$127.35	$127.30
7 purchase totals =	$751.83		$817.7453	$817.75	$817.75	$817.60