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	$62.91	10.818%	$69.7156	$69.72	$69.70	$69.70
Purchase #2	$146.59	12.370%	$164.7232	$164.72	$164.70	$164.70
Purchase #3	$56.71	5.599%	$59.8852	$59.89	$59.90	$59.90
Purchase #4	$169.39	3.527%	$175.3644	$175.36	$175.35	$175.40
Purchase #5	$140.49	11.734%	$156.9751	$156.98	$157.00	$157.00
Purchase #6	$180.76	4.720%	$189.2919	$189.29	$189.30	$189.30
Purchase #7	$170.45	4.788%	$178.6111	$178.61	$178.60	$178.60
7 purchase totals =	$927.30		$994.5665	$994.57	$994.55	$994.60