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	$56.84	9.622%	$62.3091	$62.31	$62.30	$62.30
Purchase #2	$213.30	10.835%	$236.4111	$236.41	$236.40	$236.40
Purchase #3	$74.56	10.622%	$82.4798	$82.48	$82.50	$82.50
Purchase #4	$14.57	12.861%	$16.4438	$16.44	$16.45	$16.40
Purchase #5	$126.89	12.485%	$142.7322	$142.73	$142.75	$142.70
Purchase #6	$100.68	10.634%	$111.3863	$111.39	$111.40	$111.40
Purchase #7	$96.83	4.409%	$101.0992	$101.10	$101.10	$101.10
7 purchase totals =	$683.67		$752.8615	$752.86	$752.90	$752.80