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	$205.95	4.646%	$215.5184	$215.52	$215.50	$215.50
Purchase #2	$132.60	6.127%	$140.7244	$140.72	$140.70	$140.70
Purchase #3	$165.84	12.413%	$186.4257	$186.43	$186.45	$186.40
Purchase #4	$89.41	10.119%	$98.4574	$98.46	$98.45	$98.50
Purchase #5	$201.33	7.695%	$216.8223	$216.82	$216.80	$216.80
Purchase #6	$63.29	11.550%	$70.6	$70.60	$70.60	$70.60
Purchase #7	$48.50	8.340%	$52.5449	$52.54	$52.55	$52.50
7 purchase totals =	$906.92		$981.0931	$981.09	$981.05	$981.00