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	$81.45	13.137%	$92.1501	$92.15	$92.15	$92.20
Purchase #2	$32.89	4.566%	$34.3918	$34.39	$34.40	$34.40
Purchase #3	$28.83	12.370%	$32.3963	$32.40	$32.40	$32.40
Purchase #4	$143.44	5.307%	$151.0524	$151.05	$151.05	$151.10
Purchase #5	$154.46	13.856%	$175.862	$175.86	$175.85	$175.90
Purchase #6	$61.88	8.405%	$67.081	$67.08	$67.10	$67.10
Purchase #7	$204.41	11.531%	$227.9805	$227.98	$228.00	$228.00
7 purchase totals =	$707.36		$780.9141	$780.91	$780.95	$781.10