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	$43.90	13.555%	$49.8506	$49.85	$49.85	$49.90
Purchase #2	$194.85	10.249%	$214.8202	$214.82	$214.80	$214.80
Purchase #3	$124.73	13.595%	$141.687	$141.69	$141.70	$141.70
Purchase #4	$171.38	11.239%	$190.6414	$190.64	$190.65	$190.60
Purchase #5	$163.70	13.520%	$185.8322	$185.83	$185.85	$185.80
Purchase #6	$85.88	8.663%	$93.3198	$93.32	$93.30	$93.30
Purchase #7	$194.81	13.126%	$220.3808	$220.38	$220.40	$220.40
7 purchase totals =	$979.25		$1,096.5320	$1,096.53	$1,096.55	$1,096.50