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	$133.43	4.244%	$139.0928	$139.09	$139.10	$139.10
Purchase #2	$138.86	4.326%	$144.8671	$144.87	$144.85	$144.90
Purchase #3	$164.48	12.689%	$185.3509	$185.35	$185.35	$185.40
Purchase #4	$101.92	7.647%	$109.7138	$109.71	$109.70	$109.70
Purchase #5	$28.99	13.565%	$32.9225	$32.92	$32.90	$32.90
Purchase #6	$162.42	5.249%	$170.9454	$170.95	$170.95	$170.90
Purchase #7	$204.97	11.258%	$228.0455	$228.05	$228.05	$228.00
7 purchase totals =	$935.07		$1,010.9380	$1,010.94	$1,010.90	$1,010.90