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	$108.85	13.632%	$123.6884	$123.69	$123.70	$123.70
Purchase #2	$234.73	7.856%	$253.1704	$253.17	$253.15	$253.20
Purchase #3	$49.25	11.635%	$54.9802	$54.98	$55.00	$55.00
Purchase #4	$48.96	11.295%	$54.49	$54.49	$54.50	$54.50
Purchase #5	$132.50	6.310%	$140.8608	$140.86	$140.85	$140.90
Purchase #6	$145.59	10.238%	$160.4955	$160.50	$160.50	$160.50
Purchase #7	$94.31	13.802%	$107.3267	$107.33	$107.35	$107.30
7 purchase totals =	$814.19		$895.0120	$895.02	$895.05	$895.10