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	$136.55	6.370%	$145.2482	$145.25	$145.25	$145.20
Purchase #2	$225.73	9.284%	$246.6868	$246.69	$246.70	$246.70
Purchase #3	$23.70	7.178%	$25.4012	$25.40	$25.40	$25.40
Purchase #4	$80.32	12.416%	$90.2925	$90.29	$90.30	$90.30
Purchase #5	$205.90	10.488%	$227.4948	$227.49	$227.50	$227.50
Purchase #6	$155.32	7.693%	$167.2688	$167.27	$167.25	$167.30
Purchase #7	$133.45	12.857%	$150.6077	$150.61	$150.60	$150.60
7 purchase totals =	$960.97		$1,053.0000	$1,053.00	$1,053.00	$1,053.00