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	$81.52	5.169%	$85.7338	$85.73	$85.75	$85.70
Purchase #2	$57.55	13.330%	$65.2214	$65.22	$65.20	$65.20
Purchase #3	$78.67	13.433%	$89.2377	$89.24	$89.25	$89.20
Purchase #4	$180.85	13.851%	$205.8995	$205.90	$205.90	$205.90
Purchase #5	$248.78	7.360%	$267.0902	$267.09	$267.10	$267.10
Purchase #6	$125.37	12.528%	$141.0764	$141.08	$141.10	$141.10
Purchase #7	$100.70	4.871%	$105.6051	$105.61	$105.60	$105.60
7 purchase totals =	$873.44		$959.8641	$959.87	$959.90	$959.80