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	$62.67	13.707%	$71.2602	$71.26	$71.25	$71.30
Purchase #2	$200.90	7.785%	$216.5401	$216.54	$216.55	$216.50
Purchase #3	$160.54	13.855%	$182.7828	$182.78	$182.80	$182.80
Purchase #4	$173.45	10.409%	$191.5044	$191.50	$191.50	$191.50
Purchase #5	$187.49	3.821%	$194.654	$194.65	$194.65	$194.70
Purchase #6	$204.26	7.509%	$219.5979	$219.60	$219.60	$219.60
Purchase #7	$29.77	11.549%	$33.2081	$33.21	$33.20	$33.20
7 purchase totals =	$1,019.08		$1,109.5475	$1,109.54	$1,109.55	$1,109.60