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	$34.89	9.244%	$38.1152	$38.12	$38.10	$38.10
Purchase #2	$58.90	11.193%	$65.4927	$65.49	$65.50	$65.50
Purchase #3	$228.42	10.622%	$252.6828	$252.68	$252.70	$252.70
Purchase #4	$38.76	9.787%	$42.5534	$42.55	$42.55	$42.60
Purchase #5	$157.56	7.182%	$168.876	$168.88	$168.90	$168.90
Purchase #6	$202.48	9.776%	$222.2744	$222.27	$222.25	$222.30
Purchase #7	$235.45	4.676%	$246.4596	$246.46	$246.45	$246.50
7 purchase totals =	$956.46		$1,036.4541	$1,036.45	$1,036.45	$1,036.60