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	$98.25	6.293%	$104.4329	$104.43	$104.45	$104.40
Purchase #2	$48.79	3.849%	$50.6679	$50.67	$50.65	$50.70
Purchase #3	$157.28	5.496%	$165.9241	$165.92	$165.90	$165.90
Purchase #4	$101.46	3.435%	$104.9452	$104.95	$104.95	$104.90
Purchase #5	$112.43	7.384%	$120.7318	$120.73	$120.75	$120.70
Purchase #6	$99.92	4.117%	$104.0337	$104.03	$104.05	$104.00
Purchase #7	$205.46	8.174%	$222.2543	$222.25	$222.25	$222.30
7 purchase totals =	$823.59		$872.9899	$872.98	$873.00	$872.90