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	$72.37	11.299%	$80.5471	$80.55	$80.55	$80.50
Purchase #2	$114.93	11.239%	$127.847	$127.85	$127.85	$127.80
Purchase #3	$189.26	8.540%	$205.4228	$205.42	$205.40	$205.40
Purchase #4	$153.92	7.499%	$165.4625	$165.46	$165.45	$165.50
Purchase #5	$230.67	13.132%	$260.9616	$260.96	$260.95	$261.00
Purchase #6	$96.89	13.432%	$109.9043	$109.90	$109.90	$109.90
Purchase #7	$111.49	9.668%	$122.2689	$122.27	$122.25	$122.30
7 purchase totals =	$969.53		$1,072.4142	$1,072.41	$1,072.35	$1,072.40