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	$101.50	5.138%	$106.7151	$106.72	$106.70	$106.70
Purchase #2	$102.93	8.249%	$111.4207	$111.42	$111.40	$111.40
Purchase #3	$250.89	7.308%	$269.225	$269.23	$269.25	$269.20
Purchase #4	$12.70	9.284%	$13.8791	$13.88	$13.90	$13.90
Purchase #5	$162.32	10.394%	$179.1915	$179.19	$179.20	$179.20
Purchase #6	$226.76	12.246%	$254.529	$254.53	$254.55	$254.50
Purchase #7	$48.89	6.145%	$51.8943	$51.89	$51.90	$51.90
7 purchase totals =	$905.99		$986.8547	$986.86	$986.90	$986.80