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	$120.25	5.839%	$127.2714	$127.27	$127.25	$127.30
Purchase #2	$85.46	6.316%	$90.8577	$90.86	$90.85	$90.90
Purchase #3	$143.65	7.338%	$154.191	$154.19	$154.20	$154.20
Purchase #4	$42.31	5.116%	$44.4746	$44.47	$44.45	$44.50
Purchase #5	$35.26	8.746%	$38.3438	$38.34	$38.35	$38.30
Purchase #6	$179.49	7.111%	$192.2535	$192.25	$192.25	$192.30
Purchase #7	$206.82	3.785%	$214.6481	$214.65	$214.65	$214.60
7 purchase totals =	$813.24		$862.0401	$862.03	$862.00	$862.10