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	$219.61	8.735%	$238.7929	$238.79	$238.80	$238.80
Purchase #2	$66.39	7.452%	$71.3374	$71.34	$71.35	$71.30
Purchase #3	$52.94	6.819%	$56.55	$56.55	$56.55	$56.60
Purchase #4	$81.51	12.325%	$91.5561	$91.56	$91.55	$91.60
Purchase #5	$192.42	11.667%	$214.8696	$214.87	$214.85	$214.90
Purchase #6	$228.85	9.527%	$250.6525	$250.65	$250.65	$250.70
Purchase #7	$220.38	12.580%	$248.1038	$248.10	$248.10	$248.10
7 purchase totals =	$1,062.10		$1,171.8623	$1,171.86	$1,171.85	$1,172.00