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	$61.57	11.754%	$68.8069	$68.81	$68.80	$68.80
Purchase #2	$10.29	10.727%	$11.3938	$11.39	$11.40	$11.40
Purchase #3	$80.75	10.838%	$89.5017	$89.50	$89.50	$89.50
Purchase #4	$148.98	12.375%	$167.4163	$167.42	$167.40	$167.40
Purchase #5	$100.65	3.246%	$103.9171	$103.92	$103.90	$103.90
Purchase #6	$170.40	9.296%	$186.2404	$186.24	$186.25	$186.20
Purchase #7	$174.35	12.678%	$196.4541	$196.45	$196.45	$196.50
7 purchase totals =	$746.99		$823.7303	$823.73	$823.70	$823.70