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	$82.39	5.215%	$86.6866	$86.69	$86.70	$86.70
Purchase #2	$182.32	3.107%	$187.9847	$187.98	$188.00	$188.00
Purchase #3	$54.82	9.365%	$59.9539	$59.95	$59.95	$60.00
Purchase #4	$121.60	9.222%	$132.814	$132.81	$132.80	$132.80
Purchase #5	$154.59	6.479%	$164.6059	$164.61	$164.60	$164.60
Purchase #6	$75.86	12.320%	$85.206	$85.21	$85.20	$85.20
Purchase #7	$162.35	3.495%	$168.0241	$168.02	$168.00	$168.00
7 purchase totals =	$833.93		$885.2752	$885.27	$885.25	$885.30