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	$90.26	4.238%	$94.0852	$94.09	$94.10	$94.10
Purchase #2	$26.88	7.396%	$28.868	$28.87	$28.85	$28.90
Purchase #3	$242.79	8.119%	$262.5021	$262.50	$262.50	$262.50
Purchase #4	$244.65	9.856%	$268.7627	$268.76	$268.75	$268.80
Purchase #5	$32.30	3.416%	$33.4034	$33.40	$33.40	$33.40
Purchase #6	$100.29	8.781%	$109.0965	$109.10	$109.10	$109.10
Purchase #7	$106.86	4.543%	$111.7146	$111.71	$111.70	$111.70
7 purchase totals =	$844.03		$908.4325	$908.43	$908.40	$908.50