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	$152.36	10.655%	$168.594	$168.59	$168.60	$168.60
Purchase #2	$178.80	9.670%	$196.09	$196.09	$196.10	$196.10
Purchase #3	$153.38	4.109%	$159.6824	$159.68	$159.70	$159.70
Purchase #4	$134.97	4.727%	$141.35	$141.35	$141.35	$141.40
Purchase #5	$47.87	11.537%	$53.3928	$53.39	$53.40	$53.40
Purchase #6	$116.78	5.581%	$123.2975	$123.30	$123.30	$123.30
Purchase #7	$82.67	4.279%	$86.2074	$86.21	$86.20	$86.20
7 purchase totals =	$866.83		$928.6141	$928.61	$928.65	$928.70