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	$236.75	3.422%	$244.8516	$244.85	$244.85	$244.90
Purchase #2	$231.62	3.356%	$239.3932	$239.39	$239.40	$239.40
Purchase #3	$249.73	4.611%	$261.2451	$261.25	$261.25	$261.20
Purchase #4	$18.37	3.263%	$18.9694	$18.97	$18.95	$19.00
Purchase #5	$163.59	5.641%	$172.8181	$172.82	$172.80	$172.80
Purchase #6	$40.42	4.792%	$42.3569	$42.36	$42.35	$42.40
Purchase #7	$57.91	13.574%	$65.7707	$65.77	$65.75	$65.80
7 purchase totals =	$998.39		$1,045.4050	$1,045.41	$1,045.35	$1,045.50