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	$219.70	12.205%	$246.5144	$246.51	$246.50	$246.50
Purchase #2	$39.89	4.169%	$41.553	$41.55	$41.55	$41.60
Purchase #3	$142.79	5.660%	$150.8719	$150.87	$150.85	$150.90
Purchase #4	$132.26	7.577%	$142.2813	$142.28	$142.30	$142.30
Purchase #5	$40.66	5.190%	$42.7703	$42.77	$42.75	$42.80
Purchase #6	$48.74	7.397%	$52.3453	$52.35	$52.35	$52.30
Purchase #7	$70.77	11.803%	$79.123	$79.12	$79.10	$79.10
7 purchase totals =	$694.81		$755.4592	$755.45	$755.40	$755.50