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	$217.52	3.188%	$224.4545	$224.45	$224.45	$224.50
Purchase #2	$197.90	10.398%	$218.4776	$218.48	$218.50	$218.50
Purchase #3	$156.76	10.562%	$173.317	$173.32	$173.30	$173.30
Purchase #4	$167.65	10.655%	$185.5131	$185.51	$185.50	$185.50
Purchase #5	$183.49	4.787%	$192.2737	$192.27	$192.25	$192.30
Purchase #6	$146.48	6.450%	$155.928	$155.93	$155.95	$155.90
Purchase #7	$153.39	11.216%	$170.5942	$170.59	$170.60	$170.60
7 purchase totals =	$1,223.19		$1,320.5581	$1,320.55	$1,320.55	$1,320.60