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	$103.88	4.805%	$108.8714	$108.87	$108.85	$108.90
Purchase #2	$236.43	9.521%	$258.9405	$258.94	$258.95	$258.90
Purchase #3	$75.68	10.463%	$83.5984	$83.60	$83.60	$83.60
Purchase #4	$187.77	12.348%	$210.9558	$210.96	$210.95	$211.00
Purchase #5	$59.76	11.349%	$66.5422	$66.54	$66.55	$66.50
Purchase #6	$95.86	3.641%	$99.3503	$99.35	$99.35	$99.40
Purchase #7	$173.74	6.122%	$184.3764	$184.38	$184.40	$184.40
7 purchase totals =	$933.12		$1,012.6350	$1,012.64	$1,012.65	$1,012.70