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	$142.49	5.537%	$150.3797	$150.38	$150.40	$150.40
Purchase #2	$126.93	4.771%	$132.9858	$132.99	$133.00	$133.00
Purchase #3	$167.34	3.211%	$172.7133	$172.71	$172.70	$172.70
Purchase #4	$174.56	6.493%	$185.8942	$185.89	$185.90	$185.90
Purchase #5	$147.88	8.216%	$160.0298	$160.03	$160.05	$160.00
Purchase #6	$130.66	8.762%	$142.1084	$142.11	$142.10	$142.10
Purchase #7	$198.72	7.850%	$214.3195	$214.32	$214.30	$214.30
7 purchase totals =	$1,088.58		$1,158.4307	$1,158.43	$1,158.45	$1,158.40