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	$160.57	11.473%	$178.9922	$178.99	$179.00	$179.00
Purchase #2	$89.33	13.491%	$101.3815	$101.38	$101.40	$101.40
Purchase #3	$165.64	4.207%	$172.6085	$172.61	$172.60	$172.60
Purchase #4	$9.81	4.476%	$10.2491	$10.25	$10.25	$10.20
Purchase #5	$100.91	4.174%	$105.122	$105.12	$105.10	$105.10
Purchase #6	$227.62	13.601%	$258.5786	$258.58	$258.60	$258.60
Purchase #7	$122.46	7.523%	$131.6727	$131.67	$131.65	$131.70
7 purchase totals =	$876.34		$958.6046	$958.60	$958.60	$958.60