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	$211.95	10.389%	$233.9695	$233.97	$233.95	$234.00
Purchase #2	$83.81	7.528%	$90.1192	$90.12	$90.10	$90.10
Purchase #3	$101.74	10.348%	$112.2681	$112.27	$112.25	$112.30
Purchase #4	$126.82	7.597%	$136.4545	$136.45	$136.45	$136.50
Purchase #5	$157.82	11.607%	$176.1382	$176.14	$176.15	$176.10
Purchase #6	$132.80	10.220%	$146.3722	$146.37	$146.35	$146.40
Purchase #7	$190.46	3.698%	$197.5032	$197.50	$197.50	$197.50
7 purchase totals =	$1,005.40		$1,092.8249	$1,092.82	$1,092.75	$1,092.90