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	$103.72	8.234%	$112.2603	$112.26	$112.25	$112.30
Purchase #2	$24.89	6.831%	$26.5902	$26.59	$26.60	$26.60
Purchase #3	$64.50	8.238%	$69.8135	$69.81	$69.80	$69.80
Purchase #4	$127.94	13.573%	$145.3053	$145.31	$145.30	$145.30
Purchase #5	$183.74	9.335%	$200.8921	$200.89	$200.90	$200.90
Purchase #6	$20.28	4.192%	$21.1301	$21.13	$21.15	$21.10
Purchase #7	$183.85	11.821%	$205.5829	$205.58	$205.60	$205.60
7 purchase totals =	$708.92		$781.5744	$781.57	$781.60	$781.60