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	$216.42	8.162%	$234.0842	$234.08	$234.10	$234.10
Purchase #2	$130.97	7.640%	$140.9761	$140.98	$141.00	$141.00
Purchase #3	$81.39	11.159%	$90.4723	$90.47	$90.45	$90.50
Purchase #4	$50.83	5.501%	$53.6262	$53.63	$53.65	$53.60
Purchase #5	$242.39	11.834%	$271.0744	$271.07	$271.05	$271.10
Purchase #6	$134.65	11.197%	$149.7268	$149.73	$149.75	$149.70
Purchase #7	$184.92	3.366%	$191.1444	$191.14	$191.15	$191.10
7 purchase totals =	$1,041.57		$1,131.1044	$1,131.10	$1,131.15	$1,131.10