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	$63.59	6.650%	$67.8187	$67.82	$67.80	$67.80
Purchase #2	$136.61	5.563%	$144.2096	$144.21	$144.20	$144.20
Purchase #3	$147.59	6.229%	$156.7834	$156.78	$156.80	$156.80
Purchase #4	$202.61	13.624%	$230.2136	$230.21	$230.20	$230.20
Purchase #5	$235.88	13.105%	$266.7921	$266.79	$266.80	$266.80
Purchase #6	$78.74	6.124%	$83.562	$83.56	$83.55	$83.60
Purchase #7	$207.67	7.439%	$223.1186	$223.12	$223.10	$223.10
7 purchase totals =	$1,072.69		$1,172.4980	$1,172.49	$1,172.45	$1,172.50