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	$146.59	10.682%	$162.2487	$162.25	$162.25	$162.20
Purchase #2	$242.52	8.547%	$263.2482	$263.25	$263.25	$263.20
Purchase #3	$29.97	13.632%	$34.0555	$34.06	$34.05	$34.10
Purchase #4	$74.89	8.788%	$81.4713	$81.47	$81.45	$81.50
Purchase #5	$85.98	13.385%	$97.4884	$97.49	$97.50	$97.50
Purchase #6	$151.58	11.424%	$168.8965	$168.90	$168.90	$168.90
Purchase #7	$169.43	3.787%	$175.8463	$175.85	$175.85	$175.80
7 purchase totals =	$900.96		$983.2549	$983.27	$983.25	$983.20