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	$245.96	4.721%	$257.5718	$257.57	$257.55	$257.60
Purchase #2	$220.85	8.141%	$238.8294	$238.83	$238.85	$238.80
Purchase #3	$77.60	6.295%	$82.4849	$82.48	$82.50	$82.50
Purchase #4	$135.93	13.178%	$153.8429	$153.84	$153.85	$153.80
Purchase #5	$177.27	7.499%	$190.5635	$190.56	$190.55	$190.60
Purchase #6	$75.54	10.533%	$83.4966	$83.50	$83.50	$83.50
Purchase #7	$50.27	6.289%	$53.4315	$53.43	$53.45	$53.40
7 purchase totals =	$983.42		$1,060.2206	$1,060.21	$1,060.25	$1,060.20