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	$164.67	4.212%	$171.6059	$171.61	$171.60	$171.60
Purchase #2	$143.89	4.436%	$150.273	$150.27	$150.25	$150.30
Purchase #3	$14.90	5.234%	$15.6799	$15.68	$15.70	$15.70
Purchase #4	$27.65	12.725%	$31.1685	$31.17	$31.15	$31.20
Purchase #5	$224.96	12.751%	$253.6446	$253.64	$253.65	$253.60
Purchase #6	$38.38	5.834%	$40.6191	$40.62	$40.60	$40.60
Purchase #7	$45.80	8.117%	$49.5176	$49.52	$49.50	$49.50
7 purchase totals =	$660.25		$712.5086	$712.51	$712.45	$712.50