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	$119.49	3.450%	$123.6124	$123.61	$123.60	$123.60
Purchase #2	$136.81	4.838%	$143.4289	$143.43	$143.45	$143.40
Purchase #3	$12.27	8.648%	$13.3311	$13.33	$13.35	$13.30
Purchase #4	$85.74	3.157%	$88.4468	$88.45	$88.45	$88.40
Purchase #5	$162.59	9.762%	$178.462	$178.46	$178.45	$178.50
Purchase #6	$84.60	3.801%	$87.8156	$87.82	$87.80	$87.80
Purchase #7	$41.34	11.406%	$46.0552	$46.06	$46.05	$46.10
7 purchase totals =	$642.84		$681.1520	$681.16	$681.15	$681.10