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	$216.95	11.867%	$242.6955	$242.70	$242.70	$242.70
Purchase #2	$77.91	4.713%	$81.5819	$81.58	$81.60	$81.60
Purchase #3	$236.96	9.495%	$259.4594	$259.46	$259.45	$259.50
Purchase #4	$99.40	9.257%	$108.6015	$108.60	$108.60	$108.60
Purchase #5	$226.63	12.832%	$255.7112	$255.71	$255.70	$255.70
Purchase #6	$17.88	11.242%	$19.8901	$19.89	$19.90	$19.90
Purchase #7	$168.87	11.615%	$188.4843	$188.48	$188.50	$188.50
7 purchase totals =	$1,044.60		$1,156.4239	$1,156.42	$1,156.45	$1,156.50