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	$211.47	13.574%	$240.1749	$240.17	$240.15	$240.20
Purchase #2	$108.38	8.773%	$117.8882	$117.89	$117.90	$117.90
Purchase #3	$143.81	9.395%	$157.3209	$157.32	$157.30	$157.30
Purchase #4	$102.34	10.553%	$113.1399	$113.14	$113.15	$113.10
Purchase #5	$152.50	13.105%	$172.4851	$172.49	$172.50	$172.50
Purchase #6	$161.26	6.352%	$171.5032	$171.50	$171.50	$171.50
Purchase #7	$30.91	7.308%	$33.1689	$33.17	$33.15	$33.20
7 purchase totals =	$910.67		$1,005.6811	$1,005.68	$1,005.65	$1,005.70