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	$160.64	11.692%	$179.422	$179.42	$179.40	$179.40
Purchase #2	$236.34	12.673%	$266.2914	$266.29	$266.30	$266.30
Purchase #3	$168.39	6.706%	$179.6822	$179.68	$179.70	$179.70
Purchase #4	$239.61	8.209%	$259.2796	$259.28	$259.30	$259.30
Purchase #5	$242.83	10.524%	$268.3854	$268.39	$268.40	$268.40
Purchase #6	$179.75	6.135%	$190.7777	$190.78	$190.80	$190.80
Purchase #7	$94.33	5.495%	$99.5134	$99.51	$99.50	$99.50
7 purchase totals =	$1,321.89		$1,443.3517	$1,443.35	$1,443.40	$1,443.40