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	$238.39	10.285%	$262.9084	$262.91	$262.90	$262.90
Purchase #2	$181.67	12.797%	$204.9183	$204.92	$204.90	$204.90
Purchase #3	$124.70	10.235%	$137.463	$137.46	$137.45	$137.50
Purchase #4	$15.37	8.260%	$16.6396	$16.64	$16.65	$16.60
Purchase #5	$210.27	6.505%	$223.9481	$223.95	$223.95	$223.90
Purchase #6	$200.72	13.357%	$227.5302	$227.53	$227.55	$227.50
Purchase #7	$11.53	5.629%	$12.179	$12.18	$12.20	$12.20
7 purchase totals =	$982.65		$1,085.5866	$1,085.59	$1,085.60	$1,085.50