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	$124.52	5.692%	$131.6077	$131.61	$131.60	$131.60
Purchase #2	$149.46	10.579%	$165.2714	$165.27	$165.25	$165.30
Purchase #3	$12.49	12.199%	$14.0137	$14.01	$14.00	$14.00
Purchase #4	$98.61	13.402%	$111.8257	$111.83	$111.85	$111.80
Purchase #5	$32.68	13.493%	$37.0895	$37.09	$37.10	$37.10
Purchase #6	$140.58	11.630%	$156.9295	$156.93	$156.95	$156.90
Purchase #7	$173.36	11.268%	$192.8942	$192.89	$192.90	$192.90
7 purchase totals =	$731.70		$809.6317	$809.63	$809.65	$809.60