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	$13.78	6.323%	$14.6513	$14.65	$14.65	$14.70
Purchase #2	$64.31	8.633%	$69.8619	$69.86	$69.85	$69.90
Purchase #3	$133.54	10.740%	$147.8822	$147.88	$147.90	$147.90
Purchase #4	$178.85	3.346%	$184.8343	$184.83	$184.85	$184.80
Purchase #5	$100.87	4.701%	$105.6119	$105.61	$105.60	$105.60
Purchase #6	$154.33	12.448%	$173.541	$173.54	$173.55	$173.50
Purchase #7	$156.53	8.299%	$169.5204	$169.52	$169.50	$169.50
7 purchase totals =	$802.21		$865.9030	$865.89	$865.90	$865.90