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	$41.81	8.393%	$45.3191	$45.32	$45.30	$45.30
Purchase #2	$160.69	11.147%	$178.6021	$178.60	$178.60	$178.60
Purchase #3	$175.72	6.191%	$186.5988	$186.60	$186.60	$186.60
Purchase #4	$27.76	8.544%	$30.1318	$30.13	$30.15	$30.10
Purchase #5	$127.42	7.834%	$137.4021	$137.40	$137.40	$137.40
Purchase #6	$68.77	4.705%	$72.0056	$72.01	$72.00	$72.00
Purchase #7	$66.98	9.407%	$73.2808	$73.28	$73.30	$73.30
7 purchase totals =	$669.15		$723.3403	$723.34	$723.35	$723.30