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	$176.36	11.267%	$196.2305	$196.23	$196.25	$196.20
Purchase #2	$43.81	3.827%	$45.4866	$45.49	$45.50	$45.50
Purchase #3	$10.43	12.199%	$11.7024	$11.70	$11.70	$11.70
Purchase #4	$230.54	3.816%	$239.3374	$239.34	$239.35	$239.30
Purchase #5	$106.42	4.766%	$111.492	$111.49	$111.50	$111.50
Purchase #6	$249.59	7.839%	$269.1554	$269.16	$269.15	$269.20
Purchase #7	$24.68	11.728%	$27.5745	$27.57	$27.55	$27.60
7 purchase totals =	$841.83		$900.9788	$900.98	$901.00	$901.00