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	$59.44	3.303%	$61.4033	$61.40	$61.40	$61.40
Purchase #2	$143.68	6.710%	$153.3209	$153.32	$153.30	$153.30
Purchase #3	$190.90	7.638%	$205.4809	$205.48	$205.50	$205.50
Purchase #4	$82.33	9.585%	$90.2213	$90.22	$90.20	$90.20
Purchase #5	$212.70	10.234%	$234.4677	$234.47	$234.45	$234.50
Purchase #6	$182.66	5.668%	$193.0132	$193.01	$193.00	$193.00
Purchase #7	$179.85	13.207%	$203.6028	$203.60	$203.60	$203.60
7 purchase totals =	$1,051.56		$1,141.5101	$1,141.50	$1,141.45	$1,141.50