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	$182.53	12.469%	$205.2897	$205.29	$205.30	$205.30
Purchase #2	$35.60	5.436%	$37.5352	$37.54	$37.55	$37.50
Purchase #3	$160.96	7.282%	$172.6811	$172.68	$172.70	$172.70
Purchase #4	$167.27	9.590%	$183.3112	$183.31	$183.30	$183.30
Purchase #5	$45.53	4.556%	$47.6043	$47.60	$47.60	$47.60
Purchase #6	$53.46	11.460%	$59.5865	$59.59	$59.60	$59.60
Purchase #7	$150.28	8.827%	$163.5452	$163.55	$163.55	$163.50
7 purchase totals =	$795.63		$869.5532	$869.56	$869.60	$869.50