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	$184.96	7.856%	$199.4905	$199.49	$199.50	$199.50
Purchase #2	$247.75	5.841%	$262.2211	$262.22	$262.20	$262.20
Purchase #3	$148.40	11.115%	$164.8947	$164.89	$164.90	$164.90
Purchase #4	$173.50	8.368%	$188.0185	$188.02	$188.00	$188.00
Purchase #5	$236.39	8.422%	$256.2988	$256.30	$256.30	$256.30
Purchase #6	$96.82	3.138%	$99.8582	$99.86	$99.85	$99.90
Purchase #7	$52.45	8.140%	$56.7194	$56.72	$56.70	$56.70
7 purchase totals =	$1,140.27		$1,227.5012	$1,227.50	$1,227.45	$1,227.50