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	$152.51	9.683%	$167.2775	$167.28	$167.30	$167.30
Purchase #2	$212.73	3.634%	$220.4606	$220.46	$220.45	$220.50
Purchase #3	$146.47	12.280%	$164.4565	$164.46	$164.45	$164.50
Purchase #4	$64.72	8.254%	$70.062	$70.06	$70.05	$70.10
Purchase #5	$71.26	10.396%	$78.6682	$78.67	$78.65	$78.70
Purchase #6	$198.91	13.575%	$225.912	$225.91	$225.90	$225.90
Purchase #7	$216.61	10.226%	$238.7605	$238.76	$238.75	$238.80
7 purchase totals =	$1,063.21		$1,165.5973	$1,165.60	$1,165.55	$1,165.80