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	$55.82	3.850%	$57.9691	$57.97	$57.95	$58.00
Purchase #2	$103.55	6.849%	$110.6421	$110.64	$110.65	$110.60
Purchase #3	$107.25	8.727%	$116.6097	$116.61	$116.60	$116.60
Purchase #4	$52.60	4.670%	$55.0564	$55.06	$55.05	$55.10
Purchase #5	$220.32	9.186%	$240.5586	$240.56	$240.55	$240.60
Purchase #6	$184.29	4.688%	$192.9295	$192.93	$192.95	$192.90
Purchase #7	$240.90	10.345%	$265.8211	$265.82	$265.80	$265.80
7 purchase totals =	$964.73		$1,039.5865	$1,039.59	$1,039.55	$1,039.60