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	$196.73	10.537%	$217.4594	$217.46	$217.45	$217.50
Purchase #2	$70.82	6.312%	$75.2902	$75.29	$75.30	$75.30
Purchase #3	$134.33	9.367%	$146.9127	$146.91	$146.90	$146.90
Purchase #4	$165.45	13.497%	$187.7808	$187.78	$187.80	$187.80
Purchase #5	$148.82	10.363%	$164.2422	$164.24	$164.25	$164.20
Purchase #6	$132.33	4.509%	$138.2968	$138.30	$138.30	$138.30
Purchase #7	$222.84	8.740%	$242.3162	$242.32	$242.30	$242.30
7 purchase totals =	$1,071.32		$1,172.2983	$1,172.30	$1,172.30	$1,172.30