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	$234.28	8.686%	$254.6296	$254.63	$254.65	$254.60
Purchase #2	$222.93	11.768%	$249.1644	$249.16	$249.15	$249.20
Purchase #3	$48.41	6.620%	$51.6147	$51.61	$51.60	$51.60
Purchase #4	$191.73	4.585%	$200.5208	$200.52	$200.50	$200.50
Purchase #5	$58.32	10.184%	$64.2593	$64.26	$64.25	$64.30
Purchase #6	$79.47	12.480%	$89.3879	$89.39	$89.40	$89.40
Purchase #7	$34.42	9.818%	$37.7994	$37.80	$37.80	$37.80
7 purchase totals =	$869.56		$947.3761	$947.37	$947.35	$947.40