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	$127.84	12.725%	$144.1076	$144.11	$144.10	$144.10
Purchase #2	$125.25	12.623%	$141.0603	$141.06	$141.05	$141.10
Purchase #3	$32.27	6.504%	$34.3688	$34.37	$34.35	$34.40
Purchase #4	$225.77	7.759%	$243.2875	$243.29	$243.30	$243.30
Purchase #5	$238.97	10.267%	$263.505	$263.51	$263.50	$263.50
Purchase #6	$224.63	8.723%	$244.2245	$244.22	$244.20	$244.20
Purchase #7	$176.87	13.588%	$200.9031	$200.90	$200.90	$200.90
7 purchase totals =	$1,151.60		$1,271.4568	$1,271.46	$1,271.40	$1,271.50