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	$233.35	3.264%	$240.9665	$240.97	$240.95	$241.00
Purchase #2	$77.51	10.514%	$85.6594	$85.66	$85.65	$85.70
Purchase #3	$80.63	10.866%	$89.3913	$89.39	$89.40	$89.40
Purchase #4	$150.35	5.836%	$159.1244	$159.12	$159.10	$159.10
Purchase #5	$55.68	13.385%	$63.1328	$63.13	$63.15	$63.10
Purchase #6	$204.46	11.263%	$227.4883	$227.49	$227.50	$227.50
Purchase #7	$229.37	12.320%	$257.6284	$257.63	$257.65	$257.60
7 purchase totals =	$1,031.35		$1,123.3911	$1,123.39	$1,123.40	$1,123.40