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	$30.94	7.395%	$33.228	$33.23	$33.25	$33.20
Purchase #2	$129.80	3.671%	$134.565	$134.57	$134.55	$134.60
Purchase #3	$31.61	5.499%	$33.3482	$33.35	$33.35	$33.30
Purchase #4	$109.32	8.373%	$118.4734	$118.47	$118.45	$118.50
Purchase #5	$186.71	7.118%	$200	$200.00	$200.00	$200.00
Purchase #6	$78.51	5.495%	$82.8241	$82.82	$82.80	$82.80
Purchase #7	$228.89	4.515%	$239.2244	$239.22	$239.20	$239.20
7 purchase totals =	$795.78		$841.6631	$841.66	$841.60	$841.60