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	$128.51	3.428%	$132.9153	$132.92	$132.90	$132.90
Purchase #2	$58.68	10.692%	$64.9541	$64.95	$64.95	$65.00
Purchase #3	$145.54	13.139%	$164.6625	$164.66	$164.65	$164.70
Purchase #4	$143.38	12.789%	$161.7169	$161.72	$161.70	$161.70
Purchase #5	$219.86	6.212%	$233.5177	$233.52	$233.50	$233.50
Purchase #6	$210.97	10.575%	$233.2801	$233.28	$233.30	$233.30
Purchase #7	$92.41	9.844%	$101.5068	$101.51	$101.50	$101.50
7 purchase totals =	$999.35		$1,092.5534	$1,092.56	$1,092.50	$1,092.60