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	$128.65	8.171%	$139.162	$139.16	$139.15	$139.20
Purchase #2	$72.93	6.192%	$77.4458	$77.45	$77.45	$77.40
Purchase #3	$166.98	11.151%	$185.5999	$185.60	$185.60	$185.60
Purchase #4	$93.74	10.713%	$103.7824	$103.78	$103.80	$103.80
Purchase #5	$214.93	4.253%	$224.071	$224.07	$224.05	$224.10
Purchase #6	$162.77	10.424%	$179.7371	$179.74	$179.75	$179.70
Purchase #7	$242.46	5.779%	$256.4718	$256.47	$256.45	$256.50
7 purchase totals =	$1,082.46		$1,166.2700	$1,166.27	$1,166.25	$1,166.30