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	$191.90	8.689%	$208.5742	$208.57	$208.55	$208.60
Purchase #2	$185.95	10.342%	$205.1809	$205.18	$205.20	$205.20
Purchase #3	$24.96	9.166%	$27.2478	$27.25	$27.25	$27.20
Purchase #4	$137.42	13.478%	$155.9415	$155.94	$155.95	$155.90
Purchase #5	$88.78	13.572%	$100.8292	$100.83	$100.85	$100.80
Purchase #6	$155.34	12.283%	$174.4204	$174.42	$174.40	$174.40
Purchase #7	$89.33	6.479%	$95.1177	$95.12	$95.10	$95.10
7 purchase totals =	$873.68		$967.3117	$967.31	$967.30	$967.20