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	$99.29	11.294%	$110.5038	$110.50	$110.50	$110.50
Purchase #2	$197.98	9.872%	$217.5246	$217.52	$217.50	$217.50
Purchase #3	$127.28	9.811%	$139.7674	$139.77	$139.75	$139.80
Purchase #4	$80.65	11.674%	$90.0651	$90.07	$90.05	$90.10
Purchase #5	$165.48	12.111%	$185.5213	$185.52	$185.50	$185.50
Purchase #6	$43.97	5.493%	$46.3853	$46.39	$46.40	$46.40
Purchase #7	$150.58	4.737%	$157.713	$157.71	$157.70	$157.70
7 purchase totals =	$865.23		$947.4805	$947.48	$947.40	$947.50