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	$51.68	12.409%	$58.093	$58.09	$58.10	$58.10
Purchase #2	$152.90	9.254%	$167.0494	$167.05	$167.05	$167.00
Purchase #3	$100.34	10.801%	$111.1777	$111.18	$111.20	$111.20
Purchase #4	$16.90	10.687%	$18.7061	$18.71	$18.70	$18.70
Purchase #5	$240.42	10.260%	$265.0871	$265.09	$265.10	$265.10
Purchase #6	$173.72	12.534%	$195.4941	$195.49	$195.50	$195.50
Purchase #7	$241.93	11.358%	$269.4084	$269.41	$269.40	$269.40
7 purchase totals =	$977.89		$1,085.0158	$1,085.02	$1,085.05	$1,085.00