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	$103.75	13.613%	$117.8735	$117.87	$117.85	$117.90
Purchase #2	$47.94	12.428%	$53.898	$53.90	$53.90	$53.90
Purchase #3	$133.97	5.136%	$140.8507	$140.85	$140.85	$140.90
Purchase #4	$239.71	8.625%	$260.385	$260.39	$260.40	$260.40
Purchase #5	$48.88	9.629%	$53.5867	$53.59	$53.60	$53.60
Purchase #6	$29.41	7.168%	$31.5181	$31.52	$31.50	$31.50
Purchase #7	$156.95	12.415%	$176.4353	$176.44	$176.45	$176.40
7 purchase totals =	$760.61		$834.5473	$834.56	$834.55	$834.60