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	$118.36	7.706%	$127.4808	$127.48	$127.50	$127.50
Purchase #2	$194.38	13.145%	$219.9313	$219.93	$219.95	$219.90
Purchase #3	$11.86	4.481%	$12.3914	$12.39	$12.40	$12.40
Purchase #4	$142.86	5.816%	$151.1687	$151.17	$151.15	$151.20
Purchase #5	$137.47	4.433%	$143.564	$143.56	$143.55	$143.60
Purchase #6	$18.96	13.649%	$21.5479	$21.55	$21.55	$21.50
Purchase #7	$221.40	6.175%	$235.0715	$235.07	$235.05	$235.10
7 purchase totals =	$845.29		$911.1556	$911.15	$911.15	$911.20