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	$220.32	6.140%	$233.8476	$233.85	$233.85	$233.80
Purchase #2	$174.83	9.381%	$191.2308	$191.23	$191.25	$191.20
Purchase #3	$76.39	6.223%	$81.1437	$81.14	$81.15	$81.10
Purchase #4	$11.51	6.862%	$12.2998	$12.30	$12.30	$12.30
Purchase #5	$233.55	6.769%	$249.359	$249.36	$249.35	$249.40
Purchase #6	$37.38	13.338%	$42.3657	$42.37	$42.35	$42.40
Purchase #7	$249.54	10.125%	$274.8059	$274.81	$274.80	$274.80
7 purchase totals =	$1,003.52		$1,085.0525	$1,085.06	$1,085.05	$1,085.00