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	$173.34	3.406%	$179.244	$179.24	$179.25	$179.20
Purchase #2	$69.32	4.261%	$72.2737	$72.27	$72.25	$72.30
Purchase #3	$186.40	5.174%	$196.0443	$196.04	$196.05	$196.00
Purchase #4	$134.32	5.672%	$141.9386	$141.94	$141.95	$141.90
Purchase #5	$116.36	6.763%	$124.2294	$124.23	$124.25	$124.20
Purchase #6	$137.43	12.469%	$154.5661	$154.57	$154.55	$154.60
Purchase #7	$28.80	8.748%	$31.3194	$31.32	$31.30	$31.30
7 purchase totals =	$845.97		$899.6155	$899.61	$899.60	$899.50