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	$236.89	5.695%	$250.3809	$250.38	$250.40	$250.40
Purchase #2	$173.85	6.469%	$185.0964	$185.10	$185.10	$185.10
Purchase #3	$147.82	7.114%	$158.3359	$158.34	$158.35	$158.30
Purchase #4	$168.45	3.593%	$174.5024	$174.50	$174.50	$174.50
Purchase #5	$6.68	10.597%	$7.3879	$7.39	$7.40	$7.40
Purchase #6	$132.88	13.171%	$150.3816	$150.38	$150.40	$150.40
Purchase #7	$49.76	9.368%	$54.4215	$54.42	$54.40	$54.40
7 purchase totals =	$916.33		$980.5066	$980.51	$980.55	$980.50