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	$57.88	4.229%	$60.3277	$60.33	$60.35	$60.30
Purchase #2	$167.60	5.321%	$176.518	$176.52	$176.50	$176.50
Purchase #3	$19.85	6.337%	$21.1079	$21.11	$21.10	$21.10
Purchase #4	$12.78	6.604%	$13.624	$13.62	$13.60	$13.60
Purchase #5	$224.89	13.367%	$254.951	$254.95	$254.95	$255.00
Purchase #6	$214.81	3.566%	$222.4701	$222.47	$222.45	$222.50
Purchase #7	$38.52	10.339%	$42.5026	$42.50	$42.50	$42.50
7 purchase totals =	$736.33		$791.5013	$791.50	$791.45	$791.50