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	$76.58	7.133%	$82.0425	$82.04	$82.05	$82.00
Purchase #2	$34.79	6.804%	$37.1571	$37.16	$37.15	$37.20
Purchase #3	$120.38	5.684%	$127.2224	$127.22	$127.20	$127.20
Purchase #4	$171.81	5.246%	$180.8232	$180.82	$180.80	$180.80
Purchase #5	$57.83	7.368%	$62.0909	$62.09	$62.10	$62.10
Purchase #6	$119.97	11.822%	$134.1529	$134.15	$134.15	$134.20
Purchase #7	$28.81	6.799%	$30.7688	$30.77	$30.75	$30.80
7 purchase totals =	$610.17		$654.2578	$654.25	$654.20	$654.30