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	$231.83	13.339%	$262.7538	$262.75	$262.75	$262.80
Purchase #2	$135.53	12.204%	$152.0701	$152.07	$152.05	$152.10
Purchase #3	$97.96	7.204%	$105.017	$105.02	$105.00	$105.00
Purchase #4	$104.96	13.119%	$118.7297	$118.73	$118.75	$118.70
Purchase #5	$240.82	10.292%	$265.6052	$265.61	$265.60	$265.60
Purchase #6	$201.96	9.503%	$221.1523	$221.15	$221.15	$221.20
Purchase #7	$65.76	8.120%	$71.0997	$71.10	$71.10	$71.10
7 purchase totals =	$1,078.82		$1,196.4278	$1,196.43	$1,196.40	$1,196.50