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	$107.25	10.786%	$118.818	$118.82	$118.80	$118.80
Purchase #2	$146.78	11.648%	$163.8769	$163.88	$163.90	$163.90
Purchase #3	$199.87	3.772%	$207.4091	$207.41	$207.40	$207.40
Purchase #4	$225.85	7.272%	$242.2738	$242.27	$242.25	$242.30
Purchase #5	$133.79	6.267%	$142.1746	$142.17	$142.15	$142.20
Purchase #6	$139.64	13.571%	$158.5905	$158.59	$158.60	$158.60
Purchase #7	$89.99	10.588%	$99.5181	$99.52	$99.50	$99.50
7 purchase totals =	$1,043.17		$1,132.6610	$1,132.66	$1,132.60	$1,132.70