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	$59.60	12.866%	$67.2681	$67.27	$67.25	$67.30
Purchase #2	$222.44	7.460%	$239.034	$239.03	$239.05	$239.00
Purchase #3	$60.75	11.679%	$67.845	$67.85	$67.85	$67.80
Purchase #4	$76.60	11.656%	$85.5285	$85.53	$85.55	$85.50
Purchase #5	$136.42	11.562%	$152.1929	$152.19	$152.20	$152.20
Purchase #6	$177.83	6.368%	$189.1542	$189.15	$189.15	$189.20
Purchase #7	$175.53	9.567%	$192.323	$192.32	$192.30	$192.30
7 purchase totals =	$909.17		$993.3457	$993.34	$993.35	$993.30