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	$152.66	10.447%	$168.6084	$168.61	$168.60	$168.60
Purchase #2	$245.63	10.594%	$271.652	$271.65	$271.65	$271.70
Purchase #3	$243.28	5.530%	$256.7334	$256.73	$256.75	$256.70
Purchase #4	$161.66	6.830%	$172.7014	$172.70	$172.70	$172.70
Purchase #5	$152.40	12.509%	$171.4637	$171.46	$171.45	$171.50
Purchase #6	$181.69	4.207%	$189.3337	$189.33	$189.35	$189.30
Purchase #7	$93.27	13.472%	$105.8353	$105.84	$105.85	$105.80
7 purchase totals =	$1,230.59		$1,336.3279	$1,336.32	$1,336.35	$1,336.30