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	$217.38	8.786%	$236.479	$236.48	$236.50	$236.50
Purchase #2	$84.61	3.187%	$87.3065	$87.31	$87.30	$87.30
Purchase #3	$105.27	7.611%	$113.2821	$113.28	$113.30	$113.30
Purchase #4	$225.26	11.756%	$251.7416	$251.74	$251.75	$251.70
Purchase #5	$48.30	13.590%	$54.864	$54.86	$54.85	$54.90
Purchase #6	$227.45	12.224%	$255.2535	$255.25	$255.25	$255.30
Purchase #7	$196.29	13.814%	$223.4055	$223.41	$223.40	$223.40
7 purchase totals =	$1,104.56		$1,222.3322	$1,222.33	$1,222.35	$1,222.40