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	$129.49	7.639%	$139.3817	$139.38	$139.40	$139.40
Purchase #2	$173.34	9.113%	$189.1365	$189.14	$189.15	$189.10
Purchase #3	$242.69	13.652%	$275.822	$275.82	$275.80	$275.80
Purchase #4	$92.56	13.841%	$105.3712	$105.37	$105.35	$105.40
Purchase #5	$140.99	10.335%	$155.5613	$155.56	$155.55	$155.60
Purchase #6	$21.39	12.150%	$23.9889	$23.99	$24.00	$24.00
Purchase #7	$173.29	11.184%	$192.6708	$192.67	$192.65	$192.70
7 purchase totals =	$973.75		$1,081.9324	$1,081.93	$1,081.90	$1,082.00