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	$77.30	6.683%	$82.466	$82.47	$82.45	$82.50
Purchase #2	$131.77	8.248%	$142.6384	$142.64	$142.65	$142.60
Purchase #3	$155.42	3.845%	$161.3959	$161.40	$161.40	$161.40
Purchase #4	$169.56	13.150%	$191.8571	$191.86	$191.85	$191.90
Purchase #5	$221.51	12.622%	$249.469	$249.47	$249.45	$249.50
Purchase #6	$152.76	12.784%	$172.2888	$172.29	$172.30	$172.30
Purchase #7	$177.35	4.604%	$185.5152	$185.52	$185.50	$185.50
7 purchase totals =	$1,085.67		$1,185.6304	$1,185.65	$1,185.60	$1,185.70