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	$54.64	5.181%	$57.4709	$57.47	$57.45	$57.50
Purchase #2	$123.31	3.714%	$127.8897	$127.89	$127.90	$127.90
Purchase #3	$236.75	9.113%	$258.325	$258.33	$258.35	$258.30
Purchase #4	$22.87	4.551%	$23.9108	$23.91	$23.90	$23.90
Purchase #5	$190.38	9.738%	$208.9192	$208.92	$208.90	$208.90
Purchase #6	$187.76	10.827%	$208.0888	$208.09	$208.10	$208.10
Purchase #7	$52.97	12.395%	$59.5356	$59.54	$59.55	$59.50
7 purchase totals =	$868.68		$944.1400	$944.15	$944.15	$944.10