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	$186.55	6.610%	$198.881	$198.88	$198.90	$198.90
Purchase #2	$12.72	5.801%	$13.4579	$13.46	$13.45	$13.50
Purchase #3	$248.64	9.146%	$271.3806	$271.38	$271.40	$271.40
Purchase #4	$74.55	5.130%	$78.3744	$78.37	$78.35	$78.40
Purchase #5	$216.29	10.486%	$238.9702	$238.97	$238.95	$239.00
Purchase #6	$38.87	9.714%	$42.6458	$42.65	$42.65	$42.60
Purchase #7	$232.32	8.359%	$251.7396	$251.74	$251.75	$251.70
7 purchase totals =	$1,009.94		$1,095.4495	$1,095.45	$1,095.45	$1,095.50