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	$165.98	9.833%	$182.3008	$182.30	$182.30	$182.30
Purchase #2	$89.60	12.205%	$100.5357	$100.54	$100.55	$100.50
Purchase #3	$49.47	6.222%	$52.548	$52.55	$52.55	$52.50
Purchase #4	$9.53	13.462%	$10.8129	$10.81	$10.80	$10.80
Purchase #5	$167.28	12.167%	$187.633	$187.63	$187.65	$187.60
Purchase #6	$85.45	4.696%	$89.4627	$89.46	$89.45	$89.50
Purchase #7	$244.46	3.579%	$253.2092	$253.21	$253.20	$253.20
7 purchase totals =	$811.77		$876.5023	$876.50	$876.50	$876.40