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	$31.94	10.846%	$35.4042	$35.40	$35.40	$35.40
Purchase #2	$145.59	3.122%	$150.1353	$150.14	$150.15	$150.10
Purchase #3	$144.76	8.306%	$156.7838	$156.78	$156.80	$156.80
Purchase #4	$57.46	13.717%	$65.3418	$65.34	$65.35	$65.30
Purchase #5	$67.82	11.383%	$75.54	$75.54	$75.55	$75.50
Purchase #6	$82.91	13.574%	$94.1642	$94.16	$94.15	$94.20
Purchase #7	$150.60	5.483%	$158.8574	$158.86	$158.85	$158.90
7 purchase totals =	$681.08		$736.2267	$736.22	$736.25	$736.20