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	$71.86	3.825%	$74.6086	$74.61	$74.60	$74.60
Purchase #2	$31.30	8.553%	$33.9771	$33.98	$34.00	$34.00
Purchase #3	$164.89	12.628%	$185.7123	$185.71	$185.70	$185.70
Purchase #4	$153.31	9.450%	$167.7978	$167.80	$167.80	$167.80
Purchase #5	$168.79	12.868%	$190.5099	$190.51	$190.50	$190.50
Purchase #6	$100.84	10.804%	$111.7348	$111.73	$111.75	$111.70
Purchase #7	$245.45	8.809%	$267.0717	$267.07	$267.05	$267.10
7 purchase totals =	$936.44		$1,031.4122	$1,031.41	$1,031.40	$1,031.40