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	$152.66	6.431%	$162.4776	$162.48	$162.50	$162.50
Purchase #2	$63.64	5.119%	$66.8977	$66.90	$66.90	$66.90
Purchase #3	$162.32	3.499%	$167.9996	$168.00	$168.00	$168.00
Purchase #4	$38.96	9.127%	$42.5159	$42.52	$42.50	$42.50
Purchase #5	$196.89	6.465%	$209.6189	$209.62	$209.60	$209.60
Purchase #6	$141.88	11.549%	$158.2657	$158.27	$158.25	$158.30
Purchase #7	$55.94	10.155%	$61.6207	$61.62	$61.60	$61.60
7 purchase totals =	$812.29		$869.3961	$869.41	$869.35	$869.40