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	$107.84	11.181%	$119.8976	$119.90	$119.90	$119.90
Purchase #2	$224.57	7.136%	$240.5953	$240.60	$240.60	$240.60
Purchase #3	$153.65	12.574%	$172.97	$172.97	$172.95	$173.00
Purchase #4	$98.87	11.112%	$109.8564	$109.86	$109.85	$109.90
Purchase #5	$136.57	10.288%	$150.6203	$150.62	$150.60	$150.60
Purchase #6	$184.38	4.221%	$192.1627	$192.16	$192.15	$192.20
Purchase #7	$22.96	5.839%	$24.3006	$24.30	$24.30	$24.30
7 purchase totals =	$928.84		$1,010.4029	$1,010.41	$1,010.35	$1,010.50