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	$149.84	12.425%	$168.4576	$168.46	$168.45	$168.50
Purchase #2	$156.83	4.846%	$164.43	$164.43	$164.45	$164.40
Purchase #3	$148.33	3.412%	$153.391	$153.39	$153.40	$153.40
Purchase #4	$180.38	13.738%	$205.1606	$205.16	$205.15	$205.20
Purchase #5	$58.26	11.465%	$64.9395	$64.94	$64.95	$64.90
Purchase #6	$116.68	5.582%	$123.1931	$123.19	$123.20	$123.20
Purchase #7	$30.27	8.845%	$32.9474	$32.95	$32.95	$32.90
7 purchase totals =	$840.59		$912.5192	$912.52	$912.55	$912.50