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	$143.49	9.865%	$157.6453	$157.65	$157.65	$157.60
Purchase #2	$73.27	10.658%	$81.0791	$81.08	$81.10	$81.10
Purchase #3	$38.69	7.253%	$41.4962	$41.50	$41.50	$41.50
Purchase #4	$143.84	6.485%	$153.168	$153.17	$153.15	$153.20
Purchase #5	$60.73	6.758%	$64.8341	$64.83	$64.85	$64.80
Purchase #6	$99.87	8.596%	$108.4548	$108.45	$108.45	$108.50
Purchase #7	$109.87	12.300%	$123.384	$123.38	$123.40	$123.40
7 purchase totals =	$669.76		$730.0615	$730.06	$730.10	$730.10