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	$59.97	7.729%	$64.6051	$64.61	$64.60	$64.60
Purchase #2	$93.62	11.644%	$104.5211	$104.52	$104.50	$104.50
Purchase #3	$27.62	8.857%	$30.0663	$30.07	$30.05	$30.10
Purchase #4	$139.91	8.872%	$152.3228	$152.32	$152.30	$152.30
Purchase #5	$173.77	4.695%	$181.9285	$181.93	$181.95	$181.90
Purchase #6	$82.85	7.596%	$89.1433	$89.14	$89.15	$89.10
Purchase #7	$102.86	5.351%	$108.364	$108.36	$108.35	$108.40
7 purchase totals =	$680.60		$730.9511	$730.95	$730.90	$730.90