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	$100.67	10.831%	$111.5736	$111.57	$111.55	$111.60
Purchase #2	$85.94	5.451%	$90.6246	$90.62	$90.60	$90.60
Purchase #3	$247.31	10.352%	$272.9115	$272.91	$272.90	$272.90
Purchase #4	$158.90	11.202%	$176.7	$176.70	$176.70	$176.70
Purchase #5	$95.89	4.369%	$100.0794	$100.08	$100.10	$100.10
Purchase #6	$8.46	9.376%	$9.2532	$9.25	$9.25	$9.30
Purchase #7	$228.41	13.415%	$259.0512	$259.05	$259.05	$259.10
7 purchase totals =	$925.58		$1,020.1935	$1,020.18	$1,020.15	$1,020.30