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	$84.56	7.445%	$90.8555	$90.86	$90.85	$90.90
Purchase #2	$153.88	3.823%	$159.7628	$159.76	$159.75	$159.80
Purchase #3	$155.34	11.321%	$172.926	$172.93	$172.95	$172.90
Purchase #4	$24.95	3.323%	$25.7791	$25.78	$25.80	$25.80
Purchase #5	$116.30	12.694%	$131.0631	$131.06	$131.05	$131.10
Purchase #6	$139.37	8.558%	$151.2973	$151.30	$151.30	$151.30
Purchase #7	$148.88	10.341%	$164.2757	$164.28	$164.30	$164.30
7 purchase totals =	$823.28		$895.9595	$895.97	$896.00	$896.10