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	$98.66	13.425%	$111.9051	$111.91	$111.90	$111.90
Purchase #2	$60.28	9.269%	$65.8674	$65.87	$65.85	$65.90
Purchase #3	$205.99	8.103%	$222.6814	$222.68	$222.70	$222.70
Purchase #4	$102.79	11.454%	$114.5636	$114.56	$114.55	$114.60
Purchase #5	$59.54	13.222%	$67.4124	$67.41	$67.40	$67.40
Purchase #6	$34.78	5.747%	$36.7788	$36.78	$36.80	$36.80
Purchase #7	$146.75	9.304%	$160.4036	$160.40	$160.40	$160.40
7 purchase totals =	$708.79		$779.6123	$779.61	$779.60	$779.70