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	$249.57	5.766%	$263.9602	$263.96	$263.95	$264.00
Purchase #2	$240.31	5.106%	$252.5802	$252.58	$252.60	$252.60
Purchase #3	$200.73	9.406%	$219.6107	$219.61	$219.60	$219.60
Purchase #4	$78.52	10.288%	$86.5981	$86.60	$86.60	$86.60
Purchase #5	$40.89	4.136%	$42.5812	$42.58	$42.60	$42.60
Purchase #6	$186.76	9.327%	$204.1791	$204.18	$204.20	$204.20
Purchase #7	$7.54	12.274%	$8.4655	$8.47	$8.45	$8.50
7 purchase totals =	$1,004.32		$1,077.9750	$1,077.98	$1,078.00	$1,078.10