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	$190.34	10.675%	$210.6588	$210.66	$210.65	$210.70
Purchase #2	$103.96	12.503%	$116.9581	$116.96	$116.95	$117.00
Purchase #3	$130.77	9.463%	$143.1448	$143.14	$143.15	$143.10
Purchase #4	$41.41	7.574%	$44.5464	$44.55	$44.55	$44.50
Purchase #5	$219.59	13.466%	$249.16	$249.16	$249.15	$249.20
Purchase #6	$122.71	3.569%	$127.0895	$127.09	$127.10	$127.10
Purchase #7	$214.73	11.574%	$239.5829	$239.58	$239.60	$239.60
7 purchase totals =	$1,023.51		$1,131.1405	$1,131.14	$1,131.15	$1,131.20