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	$228.45	9.586%	$250.3492	$250.35	$250.35	$250.30
Purchase #2	$233.68	4.604%	$244.4386	$244.44	$244.45	$244.40
Purchase #3	$158.43	6.436%	$168.6266	$168.63	$168.65	$168.60
Purchase #4	$204.29	4.759%	$214.0122	$214.01	$214.00	$214.00
Purchase #5	$144.60	4.333%	$150.8655	$150.87	$150.85	$150.90
Purchase #6	$175.31	7.539%	$188.5266	$188.53	$188.55	$188.50
Purchase #7	$95.53	10.306%	$105.3753	$105.38	$105.40	$105.40
7 purchase totals =	$1,240.29		$1,322.1940	$1,322.21	$1,322.25	$1,322.10