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	$219.96	10.730%	$243.5617	$243.56	$243.55	$243.60
Purchase #2	$248.97	12.695%	$280.5767	$280.58	$280.60	$280.60
Purchase #3	$175.90	6.394%	$187.147	$187.15	$187.15	$187.10
Purchase #4	$186.49	9.658%	$204.5012	$204.50	$204.50	$204.50
Purchase #5	$210.40	6.425%	$223.9182	$223.92	$223.90	$223.90
Purchase #6	$18.77	7.263%	$20.1333	$20.13	$20.15	$20.10
Purchase #7	$201.96	11.268%	$224.7169	$224.72	$224.70	$224.70
7 purchase totals =	$1,262.45		$1,384.5550	$1,384.56	$1,384.55	$1,384.50