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	$42.75	10.628%	$47.2935	$47.29	$47.30	$47.30
Purchase #2	$195.26	5.583%	$206.1614	$206.16	$206.15	$206.20
Purchase #3	$237.61	5.429%	$250.5098	$250.51	$250.50	$250.50
Purchase #4	$231.96	10.111%	$255.4135	$255.41	$255.40	$255.40
Purchase #5	$50.31	8.762%	$54.7182	$54.72	$54.70	$54.70
Purchase #6	$98.28	11.649%	$109.7286	$109.73	$109.75	$109.70
Purchase #7	$105.90	13.862%	$120.5799	$120.58	$120.60	$120.60
7 purchase totals =	$962.07		$1,044.4049	$1,044.40	$1,044.40	$1,044.40