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	$227.67	7.784%	$245.3918	$245.39	$245.40	$245.40
Purchase #2	$204.69	5.412%	$215.7678	$215.77	$215.75	$215.80
Purchase #3	$41.56	4.379%	$43.3799	$43.38	$43.40	$43.40
Purchase #4	$117.46	8.783%	$127.7765	$127.78	$127.80	$127.80
Purchase #5	$29.49	9.277%	$32.2258	$32.23	$32.25	$32.20
Purchase #6	$103.50	4.494%	$108.1513	$108.15	$108.15	$108.20
Purchase #7	$18.66	11.819%	$20.8654	$20.87	$20.85	$20.90
7 purchase totals =	$743.03		$793.5585	$793.57	$793.60	$793.70