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	$40.64	6.186%	$43.154	$43.15	$43.15	$43.20
Purchase #2	$115.88	6.683%	$123.6243	$123.62	$123.60	$123.60
Purchase #3	$101.29	5.526%	$106.8873	$106.89	$106.90	$106.90
Purchase #4	$153.29	9.584%	$167.9813	$167.98	$168.00	$168.00
Purchase #5	$112.59	6.420%	$119.8183	$119.82	$119.80	$119.80
Purchase #6	$229.33	10.124%	$252.5474	$252.55	$252.55	$252.50
Purchase #7	$170.80	11.623%	$190.6521	$190.65	$190.65	$190.70
7 purchase totals =	$923.82		$1,004.6647	$1,004.66	$1,004.65	$1,004.70