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	$145.48	11.798%	$162.6437	$162.64	$162.65	$162.60
Purchase #2	$185.33	13.189%	$209.7732	$209.77	$209.75	$209.80
Purchase #3	$5.48	9.619%	$6.0071	$6.01	$6.00	$6.00
Purchase #4	$173.94	13.580%	$197.5611	$197.56	$197.55	$197.60
Purchase #5	$77.75	7.286%	$83.4149	$83.41	$83.40	$83.40
Purchase #6	$63.70	12.113%	$71.416	$71.42	$71.40	$71.40
Purchase #7	$66.66	6.735%	$71.1496	$71.15	$71.15	$71.10
7 purchase totals =	$718.34		$801.9656	$801.96	$801.90	$801.90