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	$147.64	12.577%	$166.2087	$166.21	$166.20	$166.20
Purchase #2	$158.89	9.479%	$173.9512	$173.95	$173.95	$174.00
Purchase #3	$153.35	5.870%	$162.3516	$162.35	$162.35	$162.40
Purchase #4	$173.97	3.359%	$179.8137	$179.81	$179.80	$179.80
Purchase #5	$54.80	8.236%	$59.3133	$59.31	$59.30	$59.30
Purchase #6	$12.37	7.124%	$13.2512	$13.25	$13.25	$13.30
Purchase #7	$200.98	12.346%	$225.793	$225.79	$225.80	$225.80
7 purchase totals =	$902.00		$980.6827	$980.67	$980.65	$980.80