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	$165.46	11.700%	$184.8188	$184.82	$184.80	$184.80
Purchase #2	$74.25	8.107%	$80.2694	$80.27	$80.25	$80.30
Purchase #3	$24.38	12.374%	$27.3968	$27.40	$27.40	$27.40
Purchase #4	$67.84	12.695%	$76.4523	$76.45	$76.45	$76.50
Purchase #5	$112.83	13.232%	$127.7597	$127.76	$127.75	$127.80
Purchase #6	$215.73	6.534%	$229.8258	$229.83	$229.85	$229.80
Purchase #7	$146.85	6.361%	$156.1911	$156.19	$156.20	$156.20
7 purchase totals =	$807.34		$882.7139	$882.72	$882.70	$882.80