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	$139.65	10.709%	$154.6051	$154.61	$154.60	$154.60
Purchase #2	$158.26	10.295%	$174.5529	$174.55	$174.55	$174.60
Purchase #3	$104.36	4.155%	$108.6962	$108.70	$108.70	$108.70
Purchase #4	$162.80	10.532%	$179.9461	$179.95	$179.95	$179.90
Purchase #5	$130.67	12.680%	$147.239	$147.24	$147.25	$147.20
Purchase #6	$49.25	12.173%	$55.2452	$55.25	$55.25	$55.20
Purchase #7	$82.40	9.800%	$90.4752	$90.48	$90.50	$90.50
7 purchase totals =	$827.39		$910.7597	$910.78	$910.80	$910.70