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	$199.28	5.837%	$210.912	$210.91	$210.90	$210.90
Purchase #2	$243.93	6.470%	$259.7123	$259.71	$259.70	$259.70
Purchase #3	$172.89	13.708%	$196.5898	$196.59	$196.60	$196.60
Purchase #4	$213.42	10.730%	$236.32	$236.32	$236.30	$236.30
Purchase #5	$53.50	13.558%	$60.7535	$60.75	$60.75	$60.80
Purchase #6	$138.89	9.317%	$151.8304	$151.83	$151.85	$151.80
Purchase #7	$47.87	11.277%	$53.2683	$53.27	$53.25	$53.30
7 purchase totals =	$1,069.78		$1,169.3863	$1,169.38	$1,169.35	$1,169.40