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	$119.32	10.150%	$131.431	$131.43	$131.45	$131.40
Purchase #2	$147.25	8.669%	$160.0151	$160.02	$160.00	$160.00
Purchase #3	$170.41	9.832%	$187.1647	$187.16	$187.15	$187.20
Purchase #4	$49.47	4.145%	$51.5205	$51.52	$51.50	$51.50
Purchase #5	$152.54	6.713%	$162.78	$162.78	$162.80	$162.80
Purchase #6	$234.93	13.602%	$266.8852	$266.89	$266.90	$266.90
Purchase #7	$111.68	3.680%	$115.7898	$115.79	$115.80	$115.80
7 purchase totals =	$985.60		$1,075.5863	$1,075.59	$1,075.60	$1,075.60