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	$150.76	11.574%	$168.209	$168.21	$168.20	$168.20
Purchase #2	$155.72	10.734%	$172.435	$172.44	$172.45	$172.40
Purchase #3	$211.72	8.803%	$230.3577	$230.36	$230.35	$230.40
Purchase #4	$219.46	8.695%	$238.542	$238.54	$238.55	$238.50
Purchase #5	$63.76	10.615%	$70.5281	$70.53	$70.55	$70.50
Purchase #6	$249.39	6.346%	$265.2163	$265.22	$265.20	$265.20
Purchase #7	$127.26	12.421%	$143.067	$143.07	$143.05	$143.10
7 purchase totals =	$1,178.07		$1,288.3551	$1,288.37	$1,288.35	$1,288.30