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	$213.44	6.363%	$227.0212	$227.02	$227.00	$227.00
Purchase #2	$151.62	6.750%	$161.8544	$161.85	$161.85	$161.90
Purchase #3	$169.58	8.802%	$184.5064	$184.51	$184.50	$184.50
Purchase #4	$143.52	7.545%	$154.3486	$154.35	$154.35	$154.30
Purchase #5	$120.61	5.435%	$127.1652	$127.17	$127.15	$127.20
Purchase #6	$47.37	10.113%	$52.1605	$52.16	$52.15	$52.20
Purchase #7	$144.68	5.347%	$152.416	$152.42	$152.40	$152.40
7 purchase totals =	$990.82		$1,059.4723	$1,059.48	$1,059.40	$1,059.50