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	$105.90	10.671%	$117.2006	$117.20	$117.20	$117.20
Purchase #2	$41.75	11.794%	$46.674	$46.67	$46.65	$46.70
Purchase #3	$136.61	11.640%	$152.5114	$152.51	$152.50	$152.50
Purchase #4	$137.48	6.240%	$146.0588	$146.06	$146.05	$146.10
Purchase #5	$43.62	6.805%	$46.5883	$46.59	$46.60	$46.60
Purchase #6	$170.43	6.454%	$181.4296	$181.43	$181.45	$181.40
Purchase #7	$164.91	12.714%	$185.8767	$185.88	$185.90	$185.90
7 purchase totals =	$800.70		$876.3394	$876.34	$876.35	$876.40