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	$85.59	3.337%	$88.4461	$88.45	$88.45	$88.40
Purchase #2	$67.82	4.120%	$70.6142	$70.61	$70.60	$70.60
Purchase #3	$217.86	4.384%	$227.411	$227.41	$227.40	$227.40
Purchase #4	$38.86	5.213%	$40.8858	$40.89	$40.90	$40.90
Purchase #5	$172.25	3.435%	$178.1668	$178.17	$178.15	$178.20
Purchase #6	$185.49	13.203%	$209.9802	$209.98	$210.00	$210.00
Purchase #7	$177.43	5.531%	$187.2437	$187.24	$187.25	$187.20
7 purchase totals =	$945.30		$1,002.7478	$1,002.75	$1,002.75	$1,002.70