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	$144.47	10.257%	$159.2883	$159.29	$159.30	$159.30
Purchase #2	$213.57	10.650%	$236.3152	$236.32	$236.30	$236.30
Purchase #3	$128.83	3.198%	$132.95	$132.95	$132.95	$133.00
Purchase #4	$57.43	6.692%	$61.2732	$61.27	$61.25	$61.30
Purchase #5	$214.75	4.119%	$223.5956	$223.60	$223.60	$223.60
Purchase #6	$184.97	6.356%	$196.7267	$196.73	$196.75	$196.70
Purchase #7	$9.85	12.462%	$11.0775	$11.08	$11.10	$11.10
7 purchase totals =	$953.87		$1,021.2265	$1,021.24	$1,021.25	$1,021.30