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	$225.65	10.277%	$248.8401	$248.84	$248.85	$248.80
Purchase #2	$100.76	10.570%	$111.4103	$111.41	$111.40	$111.40
Purchase #3	$208.28	10.812%	$230.7992	$230.80	$230.80	$230.80
Purchase #4	$74.98	4.612%	$78.4381	$78.44	$78.45	$78.40
Purchase #5	$89.89	8.723%	$97.7311	$97.73	$97.75	$97.70
Purchase #6	$139.99	3.282%	$144.5845	$144.58	$144.60	$144.60
Purchase #7	$19.73	5.394%	$20.7942	$20.79	$20.80	$20.80
7 purchase totals =	$859.28		$932.5975	$932.59	$932.65	$932.50