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	$190.69	9.657%	$209.1049	$209.10	$209.10	$209.10
Purchase #2	$98.52	13.171%	$111.4961	$111.50	$111.50	$111.50
Purchase #3	$20.82	4.445%	$21.7454	$21.75	$21.75	$21.70
Purchase #4	$41.68	3.291%	$43.0517	$43.05	$43.05	$43.10
Purchase #5	$247.99	3.179%	$255.8736	$255.87	$255.85	$255.90
Purchase #6	$72.70	8.384%	$78.7952	$78.80	$78.80	$78.80
Purchase #7	$160.88	11.254%	$178.9854	$178.99	$179.00	$179.00
7 purchase totals =	$833.28		$899.0523	$899.06	$899.05	$899.10