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	$178.88	7.585%	$192.448	$192.45	$192.45	$192.40
Purchase #2	$85.74	11.339%	$95.4621	$95.46	$95.45	$95.50
Purchase #3	$71.61	7.857%	$77.2364	$77.24	$77.25	$77.20
Purchase #4	$214.51	6.570%	$228.6033	$228.60	$228.60	$228.60
Purchase #5	$85.58	3.827%	$88.8551	$88.86	$88.85	$88.90
Purchase #6	$53.58	11.730%	$59.8649	$59.86	$59.85	$59.90
Purchase #7	$121.96	13.470%	$138.388	$138.39	$138.40	$138.40
7 purchase totals =	$811.86		$880.8578	$880.86	$880.85	$880.90