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	$148.79	7.522%	$159.982	$159.98	$160.00	$160.00
Purchase #2	$68.32	11.128%	$75.9226	$75.92	$75.90	$75.90
Purchase #3	$25.97	4.198%	$27.0602	$27.06	$27.05	$27.10
Purchase #4	$99.88	5.310%	$105.1836	$105.18	$105.20	$105.20
Purchase #5	$145.81	12.615%	$164.2039	$164.20	$164.20	$164.20
Purchase #6	$56.88	4.401%	$59.3833	$59.38	$59.40	$59.40
Purchase #7	$34.27	8.170%	$37.0699	$37.07	$37.05	$37.10
7 purchase totals =	$579.92		$628.8055	$628.79	$628.80	$628.90