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	$109.26	8.492%	$118.5384	$118.54	$118.55	$118.50
Purchase #2	$16.88	5.716%	$17.8449	$17.84	$17.85	$17.80
Purchase #3	$129.51	9.747%	$142.1333	$142.13	$142.15	$142.10
Purchase #4	$131.47	8.689%	$142.8934	$142.89	$142.90	$142.90
Purchase #5	$142.76	8.743%	$155.2415	$155.24	$155.25	$155.20
Purchase #6	$126.52	3.618%	$131.0975	$131.10	$131.10	$131.10
Purchase #7	$244.78	4.341%	$255.4059	$255.41	$255.40	$255.40
7 purchase totals =	$901.18		$963.1549	$963.15	$963.20	$963.00