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	$70.81	5.608%	$74.781	$74.78	$74.80	$74.80
Purchase #2	$85.98	5.715%	$90.8938	$90.89	$90.90	$90.90
Purchase #3	$112.37	11.370%	$125.1465	$125.15	$125.15	$125.10
Purchase #4	$121.64	8.368%	$131.8188	$131.82	$131.80	$131.80
Purchase #5	$135.54	5.585%	$143.1099	$143.11	$143.10	$143.10
Purchase #6	$208.36	10.539%	$230.3191	$230.32	$230.30	$230.30
Purchase #7	$155.26	11.730%	$173.472	$173.47	$173.45	$173.50
7 purchase totals =	$889.96		$969.5411	$969.54	$969.50	$969.50