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	$193.55	11.343%	$215.5044	$215.50	$215.50	$215.50
Purchase #2	$74.94	4.638%	$78.4157	$78.42	$78.40	$78.40
Purchase #3	$32.86	12.451%	$36.9514	$36.95	$36.95	$37.00
Purchase #4	$120.52	5.816%	$127.5294	$127.53	$127.55	$127.50
Purchase #5	$170.59	4.509%	$178.2819	$178.28	$178.30	$178.30
Purchase #6	$87.27	13.427%	$98.9877	$98.99	$99.00	$99.00
Purchase #7	$51.25	9.168%	$55.9486	$55.95	$55.95	$55.90
7 purchase totals =	$730.98		$791.6191	$791.62	$791.65	$791.60