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	$30.97	4.442%	$32.3457	$32.35	$32.35	$32.30
Purchase #2	$35.89	7.771%	$38.679	$38.68	$38.70	$38.70
Purchase #3	$175.60	4.201%	$182.977	$182.98	$183.00	$183.00
Purchase #4	$211.61	5.217%	$222.6497	$222.65	$222.65	$222.60
Purchase #5	$36.52	10.706%	$40.4298	$40.43	$40.45	$40.40
Purchase #6	$111.87	10.569%	$123.6935	$123.69	$123.70	$123.70
Purchase #7	$84.98	5.805%	$89.9131	$89.91	$89.90	$89.90
7 purchase totals =	$687.44		$730.6878	$730.69	$730.75	$730.60