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	$92.89	7.769%	$100.1066	$100.11	$100.10	$100.10
Purchase #2	$80.57	10.510%	$89.0379	$89.04	$89.05	$89.00
Purchase #3	$19.50	6.194%	$20.7078	$20.71	$20.70	$20.70
Purchase #4	$106.25	10.676%	$117.5933	$117.59	$117.60	$117.60
Purchase #5	$90.55	3.626%	$93.8333	$93.83	$93.85	$93.80
Purchase #6	$238.57	8.417%	$258.6504	$258.65	$258.65	$258.70
Purchase #7	$238.86	11.544%	$266.434	$266.43	$266.45	$266.40
7 purchase totals =	$867.19		$946.3633	$946.36	$946.40	$946.30