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	$181.36	8.219%	$196.266	$196.27	$196.25	$196.30
Purchase #2	$170.88	10.370%	$188.6003	$188.60	$188.60	$188.60
Purchase #3	$234.54	7.487%	$252.1	$252.10	$252.10	$252.10
Purchase #4	$48.57	10.813%	$53.8219	$53.82	$53.80	$53.80
Purchase #5	$196.53	9.753%	$215.6976	$215.70	$215.70	$215.70
Purchase #6	$145.67	10.420%	$160.8488	$160.85	$160.85	$160.80
Purchase #7	$143.83	7.687%	$154.8862	$154.89	$154.90	$154.90
7 purchase totals =	$1,121.38		$1,222.2208	$1,222.23	$1,222.20	$1,222.20