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	$227.31	3.143%	$234.4544	$234.45	$234.45	$234.50
Purchase #2	$67.52	6.763%	$72.0864	$72.09	$72.10	$72.10
Purchase #3	$160.48	12.777%	$180.9845	$180.98	$181.00	$181.00
Purchase #4	$41.55	7.607%	$44.7107	$44.71	$44.70	$44.70
Purchase #5	$152.78	6.586%	$162.8421	$162.84	$162.85	$162.80
Purchase #6	$220.67	5.102%	$231.9286	$231.93	$231.95	$231.90
Purchase #7	$99.87	5.692%	$105.5546	$105.55	$105.55	$105.60
7 purchase totals =	$970.18		$1,032.5613	$1,032.55	$1,032.60	$1,032.60