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	$225.29	4.281%	$234.9347	$234.93	$234.95	$234.90
Purchase #2	$53.40	12.146%	$59.886	$59.89	$59.90	$59.90
Purchase #3	$15.40	3.348%	$15.9156	$15.92	$15.90	$15.90
Purchase #4	$193.75	5.192%	$203.8095	$203.81	$203.80	$203.80
Purchase #5	$47.90	10.385%	$52.8744	$52.87	$52.85	$52.90
Purchase #6	$100.66	5.151%	$105.845	$105.85	$105.85	$105.80
Purchase #7	$58.90	6.680%	$62.8345	$62.83	$62.85	$62.80
7 purchase totals =	$695.30		$736.0997	$736.10	$736.10	$736.00