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	$103.65	3.748%	$107.5348	$107.53	$107.55	$107.50
Purchase #2	$29.34	5.158%	$30.8534	$30.85	$30.85	$30.90
Purchase #3	$212.34	5.287%	$223.5664	$223.57	$223.55	$223.60
Purchase #4	$54.25	10.433%	$59.9099	$59.91	$59.90	$59.90
Purchase #5	$44.98	13.144%	$50.8922	$50.89	$50.90	$50.90
Purchase #6	$88.86	5.616%	$93.8504	$93.85	$93.85	$93.90
Purchase #7	$200.39	5.165%	$210.7401	$210.74	$210.75	$210.70
7 purchase totals =	$733.81		$777.3472	$777.34	$777.35	$777.40