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	$159.47	11.805%	$178.2954	$178.30	$178.30	$178.30
Purchase #2	$38.86	9.842%	$42.6846	$42.68	$42.70	$42.70
Purchase #3	$97.70	7.195%	$104.7295	$104.73	$104.75	$104.70
Purchase #4	$137.51	10.874%	$152.4628	$152.46	$152.45	$152.50
Purchase #5	$206.87	7.862%	$223.1341	$223.13	$223.15	$223.10
Purchase #6	$237.96	7.519%	$255.8522	$255.85	$255.85	$255.90
Purchase #7	$182.87	10.173%	$201.4734	$201.47	$201.45	$201.50
7 purchase totals =	$1,061.24		$1,158.6320	$1,158.62	$1,158.65	$1,158.70