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	$89.71	5.246%	$94.4162	$94.42	$94.40	$94.40
Purchase #2	$116.67	5.523%	$123.1137	$123.11	$123.10	$123.10
Purchase #3	$217.92	4.380%	$227.4649	$227.46	$227.45	$227.50
Purchase #4	$175.48	4.849%	$183.989	$183.99	$184.00	$184.00
Purchase #5	$99.89	5.436%	$105.32	$105.32	$105.30	$105.30
Purchase #6	$229.79	10.810%	$254.6303	$254.63	$254.65	$254.60
Purchase #7	$76.39	7.202%	$81.8916	$81.89	$81.90	$81.90
7 purchase totals =	$1,005.85		$1,070.8257	$1,070.82	$1,070.80	$1,070.80