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	$160.94	4.583%	$168.3159	$168.32	$168.30	$168.30
Purchase #2	$176.76	7.239%	$189.5557	$189.56	$189.55	$189.60
Purchase #3	$237.87	5.438%	$250.8054	$250.81	$250.80	$250.80
Purchase #4	$222.75	13.868%	$253.641	$253.64	$253.65	$253.60
Purchase #5	$95.43	10.813%	$105.7488	$105.75	$105.75	$105.70
Purchase #6	$42.77	4.131%	$44.5368	$44.54	$44.55	$44.50
Purchase #7	$79.51	3.206%	$82.0591	$82.06	$82.05	$82.10
7 purchase totals =	$1,016.03		$1,094.6627	$1,094.68	$1,094.65	$1,094.60