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	$149.42	5.747%	$158.0072	$158.01	$158.00	$158.00
Purchase #2	$80.84	5.528%	$85.3088	$85.31	$85.30	$85.30
Purchase #3	$160.37	3.147%	$165.4168	$165.42	$165.40	$165.40
Purchase #4	$38.36	13.241%	$43.4392	$43.44	$43.45	$43.40
Purchase #5	$78.51	12.473%	$88.3026	$88.30	$88.30	$88.30
Purchase #6	$169.98	9.820%	$186.672	$186.67	$186.65	$186.70
Purchase #7	$173.29	4.653%	$181.3532	$181.35	$181.35	$181.40
7 purchase totals =	$850.77		$908.4998	$908.50	$908.45	$908.50