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	$61.68	6.730%	$65.8311	$65.83	$65.85	$65.80
Purchase #2	$48.98	4.720%	$51.2919	$51.29	$51.30	$51.30
Purchase #3	$108.68	3.353%	$112.324	$112.32	$112.30	$112.30
Purchase #4	$30.66	8.627%	$33.305	$33.31	$33.30	$33.30
Purchase #5	$6.84	9.539%	$7.4925	$7.49	$7.50	$7.50
Purchase #6	$126.70	11.760%	$141.5999	$141.60	$141.60	$141.60
Purchase #7	$37.42	7.649%	$40.2823	$40.28	$40.30	$40.30
7 purchase totals =	$420.96		$452.1267	$452.12	$452.15	$452.10