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	$55.59	11.282%	$61.8617	$61.86	$61.85	$61.90
Purchase #2	$204.51	6.129%	$217.0444	$217.04	$217.05	$217.00
Purchase #3	$100.51	10.308%	$110.8706	$110.87	$110.85	$110.90
Purchase #4	$74.40	8.556%	$80.7657	$80.77	$80.75	$80.80
Purchase #5	$36.90	13.156%	$41.7546	$41.75	$41.75	$41.80
Purchase #6	$50.87	7.820%	$54.848	$54.85	$54.85	$54.80
Purchase #7	$146.91	5.143%	$154.4656	$154.47	$154.45	$154.50
7 purchase totals =	$669.69		$721.6106	$721.61	$721.55	$721.70