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	$189.85	11.310%	$211.322	$211.32	$211.30	$211.30
Purchase #2	$221.39	5.863%	$234.3701	$234.37	$234.35	$234.40
Purchase #3	$157.37	5.389%	$165.8507	$165.85	$165.85	$165.90
Purchase #4	$144.97	5.126%	$152.4012	$152.40	$152.40	$152.40
Purchase #5	$48.80	12.257%	$54.7814	$54.78	$54.80	$54.80
Purchase #6	$166.48	9.677%	$182.5903	$182.59	$182.60	$182.60
Purchase #7	$150.52	13.312%	$170.5572	$170.56	$170.55	$170.60
7 purchase totals =	$1,079.38		$1,171.8729	$1,171.87	$1,171.85	$1,172.00