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	$176.61	11.600%	$197.0968	$197.10	$197.10	$197.10
Purchase #2	$210.77	11.731%	$235.4954	$235.50	$235.50	$235.50
Purchase #3	$41.77	7.855%	$45.051	$45.05	$45.05	$45.10
Purchase #4	$89.50	6.794%	$95.5806	$95.58	$95.60	$95.60
Purchase #5	$20.38	5.422%	$21.485	$21.49	$21.50	$21.50
Purchase #6	$131.49	13.509%	$149.253	$149.25	$149.25	$149.30
Purchase #7	$78.52	10.195%	$86.5251	$86.53	$86.55	$86.50
7 purchase totals =	$749.04		$830.4869	$830.50	$830.55	$830.60