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	$78.28	11.307%	$87.1311	$87.13	$87.15	$87.10
Purchase #2	$127.62	13.576%	$144.9457	$144.95	$144.95	$144.90
Purchase #3	$201.72	7.123%	$216.0885	$216.09	$216.10	$216.10
Purchase #4	$238.48	8.360%	$258.4169	$258.42	$258.40	$258.40
Purchase #5	$104.96	4.732%	$109.9267	$109.93	$109.95	$109.90
Purchase #6	$151.36	11.678%	$169.0358	$169.04	$169.05	$169.00
Purchase #7	$173.41	5.292%	$182.5869	$182.59	$182.60	$182.60
7 purchase totals =	$1,075.83		$1,168.1316	$1,168.15	$1,168.20	$1,168.00