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	$96.26	8.278%	$104.2284	$104.23	$104.25	$104.20
Purchase #2	$124.86	11.434%	$139.1365	$139.14	$139.15	$139.10
Purchase #3	$66.81	6.366%	$71.0631	$71.06	$71.05	$71.10
Purchase #4	$155.99	12.221%	$175.0535	$175.05	$175.05	$175.10
Purchase #5	$16.64	11.390%	$18.5353	$18.54	$18.55	$18.50
Purchase #6	$109.29	12.614%	$123.0758	$123.08	$123.10	$123.10
Purchase #7	$134.26	5.229%	$141.2805	$141.28	$141.30	$141.30
7 purchase totals =	$704.11		$772.3731	$772.38	$772.45	$772.40