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	$62.26	3.849%	$64.6564	$64.66	$64.65	$64.70
Purchase #2	$159.27	12.104%	$178.548	$178.55	$178.55	$178.50
Purchase #3	$157.84	11.321%	$175.7091	$175.71	$175.70	$175.70
Purchase #4	$87.45	13.204%	$98.9969	$99.00	$99.00	$99.00
Purchase #5	$139.85	8.612%	$151.8939	$151.89	$151.90	$151.90
Purchase #6	$238.28	4.693%	$249.4625	$249.46	$249.45	$249.50
Purchase #7	$176.62	4.323%	$184.2553	$184.26	$184.25	$184.30
7 purchase totals =	$1,021.57		$1,103.5221	$1,103.53	$1,103.50	$1,103.60