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	$10.42	4.548%	$10.8939	$10.89	$10.90	$10.90
Purchase #2	$187.70	5.563%	$198.1418	$198.14	$198.15	$198.10
Purchase #3	$78.98	4.402%	$82.4567	$82.46	$82.45	$82.50
Purchase #4	$148.83	6.455%	$158.437	$158.44	$158.45	$158.40
Purchase #5	$148.67	8.207%	$160.8713	$160.87	$160.85	$160.90
Purchase #6	$223.55	7.321%	$239.9161	$239.92	$239.90	$239.90
Purchase #7	$145.89	9.554%	$159.8283	$159.83	$159.85	$159.80
7 purchase totals =	$944.04		$1,010.5451	$1,010.55	$1,010.55	$1,010.50