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	$40.44	10.292%	$44.6021	$44.60	$44.60	$44.60
Purchase #2	$78.56	3.145%	$81.0307	$81.03	$81.05	$81.00
Purchase #3	$66.73	6.388%	$70.9927	$70.99	$71.00	$71.00
Purchase #4	$111.86	4.867%	$117.3042	$117.30	$117.30	$117.30
Purchase #5	$26.48	3.784%	$27.482	$27.48	$27.50	$27.50
Purchase #6	$47.39	4.238%	$49.3984	$49.40	$49.40	$49.40
Purchase #7	$127.27	11.619%	$142.0575	$142.06	$142.05	$142.10
7 purchase totals =	$498.73		$532.8676	$532.86	$532.90	$532.90