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	$173.86	9.568%	$190.4949	$190.49	$190.50	$190.50
Purchase #2	$233.85	12.159%	$262.2838	$262.28	$262.30	$262.30
Purchase #3	$180.92	6.454%	$192.5966	$192.60	$192.60	$192.60
Purchase #4	$246.63	9.846%	$270.9132	$270.91	$270.90	$270.90
Purchase #5	$77.47	10.513%	$85.6144	$85.61	$85.60	$85.60
Purchase #6	$211.76	10.445%	$233.8783	$233.88	$233.90	$233.90
Purchase #7	$63.27	4.660%	$66.2184	$66.22	$66.20	$66.20
7 purchase totals =	$1,187.76		$1,301.9996	$1,301.99	$1,302.00	$1,302.00