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	$59.68	6.129%	$63.3378	$63.34	$63.35	$63.30
Purchase #2	$101.55	4.129%	$105.743	$105.74	$105.75	$105.70
Purchase #3	$74.40	10.382%	$82.1242	$82.12	$82.10	$82.10
Purchase #4	$191.87	3.395%	$198.384	$198.38	$198.40	$198.40
Purchase #5	$103.70	7.317%	$111.2877	$111.29	$111.30	$111.30
Purchase #6	$131.79	5.502%	$139.0411	$139.04	$139.05	$139.00
Purchase #7	$51.92	3.591%	$53.7844	$53.78	$53.80	$53.80
7 purchase totals =	$714.91		$753.7022	$753.69	$753.75	$753.60