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	$36.61	5.253%	$38.5331	$38.53	$38.55	$38.50
Purchase #2	$53.69	10.249%	$59.1927	$59.19	$59.20	$59.20
Purchase #3	$11.69	7.211%	$12.533	$12.53	$12.55	$12.50
Purchase #4	$40.76	5.180%	$42.8714	$42.87	$42.85	$42.90
Purchase #5	$214.96	11.622%	$239.9427	$239.94	$239.95	$239.90
Purchase #6	$149.85	11.772%	$167.4903	$167.49	$167.50	$167.50
Purchase #7	$166.86	11.803%	$186.5545	$186.55	$186.55	$186.60
7 purchase totals =	$674.42		$747.1177	$747.10	$747.15	$747.10