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	$81.34	6.812%	$86.8809	$86.88	$86.90	$86.90
Purchase #2	$64.91	11.580%	$72.4266	$72.43	$72.45	$72.40
Purchase #3	$102.69	13.812%	$116.8735	$116.87	$116.85	$116.90
Purchase #4	$180.30	7.457%	$193.745	$193.75	$193.75	$193.70
Purchase #5	$39.56	9.326%	$43.2494	$43.25	$43.25	$43.20
Purchase #6	$46.67	6.307%	$49.6135	$49.61	$49.60	$49.60
Purchase #7	$155.95	5.741%	$164.9031	$164.90	$164.90	$164.90
7 purchase totals =	$671.42		$727.6920	$727.69	$727.70	$727.60