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	$149.56	5.405%	$157.6437	$157.64	$157.65	$157.60
Purchase #2	$235.91	3.245%	$243.5653	$243.57	$243.55	$243.60
Purchase #3	$215.87	8.178%	$233.5238	$233.52	$233.50	$233.50
Purchase #4	$184.33	6.666%	$196.6174	$196.62	$196.60	$196.60
Purchase #5	$31.37	3.597%	$32.4984	$32.50	$32.50	$32.50
Purchase #6	$75.25	3.812%	$78.1185	$78.12	$78.10	$78.10
Purchase #7	$33.79	6.798%	$36.087	$36.09	$36.10	$36.10
7 purchase totals =	$926.08		$978.0541	$978.06	$978.00	$978.00