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	$184.79	11.288%	$205.6491	$205.65	$205.65	$205.60
Purchase #2	$194.64	8.710%	$211.5931	$211.59	$211.60	$211.60
Purchase #3	$190.67	13.621%	$216.6412	$216.64	$216.65	$216.60
Purchase #4	$69.51	4.274%	$72.4809	$72.48	$72.50	$72.50
Purchase #5	$17.45	8.328%	$18.9032	$18.90	$18.90	$18.90
Purchase #6	$179.48	11.158%	$199.5064	$199.51	$199.50	$199.50
Purchase #7	$17.27	6.228%	$18.3456	$18.35	$18.35	$18.30
7 purchase totals =	$853.81		$943.1195	$943.12	$943.15	$943.00