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	$82.39	7.567%	$88.6245	$88.62	$88.60	$88.60
Purchase #2	$125.70	10.643%	$139.0783	$139.08	$139.10	$139.10
Purchase #3	$77.62	9.848%	$85.264	$85.26	$85.25	$85.30
Purchase #4	$158.61	3.797%	$164.6324	$164.63	$164.65	$164.60
Purchase #5	$155.38	11.301%	$172.9395	$172.94	$172.95	$172.90
Purchase #6	$162.43	13.615%	$184.5448	$184.54	$184.55	$184.50
Purchase #7	$232.56	5.670%	$245.7462	$245.75	$245.75	$245.70
7 purchase totals =	$994.69		$1,080.8297	$1,080.82	$1,080.85	$1,080.70