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	$63.88	13.656%	$72.6035	$72.60	$72.60	$72.60
Purchase #2	$130.73	8.733%	$142.1467	$142.15	$142.15	$142.10
Purchase #3	$76.60	9.596%	$83.9505	$83.95	$83.95	$84.00
Purchase #4	$127.69	13.761%	$145.2614	$145.26	$145.25	$145.30
Purchase #5	$190.41	10.786%	$210.9476	$210.95	$210.95	$210.90
Purchase #6	$27.29	4.374%	$28.4837	$28.48	$28.50	$28.50
Purchase #7	$184.70	5.841%	$195.4883	$195.49	$195.50	$195.50
7 purchase totals =	$801.30		$878.8817	$878.88	$878.90	$878.90