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	$96.51	4.480%	$100.8336	$100.83	$100.85	$100.80
Purchase #2	$230.49	10.321%	$254.2789	$254.28	$254.30	$254.30
Purchase #3	$172.39	10.706%	$190.8461	$190.85	$190.85	$190.80
Purchase #4	$123.85	8.872%	$134.838	$134.84	$134.85	$134.80
Purchase #5	$165.82	7.366%	$178.0343	$178.03	$178.05	$178.00
Purchase #6	$158.59	12.850%	$178.9688	$178.97	$178.95	$179.00
Purchase #7	$111.60	6.464%	$118.8138	$118.81	$118.80	$118.80
7 purchase totals =	$1,059.25		$1,156.6135	$1,156.61	$1,156.65	$1,156.50