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	$63.38	3.359%	$65.5089	$65.51	$65.50	$65.50
Purchase #2	$160.69	6.523%	$171.1718	$171.17	$171.15	$171.20
Purchase #3	$87.28	9.484%	$95.5576	$95.56	$95.55	$95.60
Purchase #4	$53.79	6.852%	$57.4757	$57.48	$57.50	$57.50
Purchase #5	$150.58	12.195%	$168.9432	$168.94	$168.95	$168.90
Purchase #6	$222.37	13.603%	$252.619	$252.62	$252.60	$252.60
Purchase #7	$175.34	8.587%	$190.3964	$190.40	$190.40	$190.40
7 purchase totals =	$913.43		$1,001.6726	$1,001.68	$1,001.65	$1,001.70