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	$233.78	5.532%	$246.7127	$246.71	$246.70	$246.70
Purchase #2	$154.63	11.272%	$172.0599	$172.06	$172.05	$172.10
Purchase #3	$64.38	6.695%	$68.6902	$68.69	$68.70	$68.70
Purchase #4	$43.98	5.167%	$46.2524	$46.25	$46.25	$46.30
Purchase #5	$101.75	3.605%	$105.4181	$105.42	$105.40	$105.40
Purchase #6	$49.28	7.761%	$53.1046	$53.10	$53.10	$53.10
Purchase #7	$150.89	11.638%	$168.4506	$168.45	$168.45	$168.50
7 purchase totals =	$798.69		$860.6885	$860.68	$860.65	$860.80