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	$237.27	7.350%	$254.7093	$254.71	$254.70	$254.70
Purchase #2	$60.55	11.373%	$67.4364	$67.44	$67.45	$67.40
Purchase #3	$116.90	9.571%	$128.0885	$128.09	$128.10	$128.10
Purchase #4	$182.89	12.604%	$205.9415	$205.94	$205.95	$205.90
Purchase #5	$19.27	6.747%	$20.5701	$20.57	$20.55	$20.60
Purchase #6	$168.93	11.574%	$188.482	$188.48	$188.50	$188.50
Purchase #7	$203.47	7.648%	$219.0314	$219.03	$219.05	$219.00
7 purchase totals =	$989.28		$1,084.2592	$1,084.26	$1,084.30	$1,084.20