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	$234.73	8.831%	$255.459	$255.46	$255.45	$255.50
Purchase #2	$106.46	5.317%	$112.1205	$112.12	$112.10	$112.10
Purchase #3	$141.69	9.291%	$154.8544	$154.85	$154.85	$154.90
Purchase #4	$139.54	11.662%	$155.8132	$155.81	$155.80	$155.80
Purchase #5	$111.56	8.232%	$120.7436	$120.74	$120.75	$120.70
Purchase #6	$127.72	7.175%	$136.8839	$136.88	$136.90	$136.90
Purchase #7	$112.39	6.770%	$119.9988	$120.00	$120.00	$120.00
7 purchase totals =	$974.09		$1,055.8734	$1,055.86	$1,055.85	$1,055.90