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	$67.73	4.822%	$70.9959	$71.00	$71.00	$71.00
Purchase #2	$170.74	9.534%	$187.0184	$187.02	$187.00	$187.00
Purchase #3	$20.71	5.111%	$21.7685	$21.77	$21.75	$21.80
Purchase #4	$61.54	3.415%	$63.6416	$63.64	$63.65	$63.60
Purchase #5	$178.86	3.808%	$185.671	$185.67	$185.65	$185.70
Purchase #6	$37.78	4.841%	$39.6089	$39.61	$39.60	$39.60
Purchase #7	$38.31	13.863%	$43.6209	$43.62	$43.60	$43.60
7 purchase totals =	$575.67		$612.3252	$612.33	$612.25	$612.30