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	$65.32	9.579%	$71.577	$71.58	$71.60	$71.60
Purchase #2	$157.30	3.310%	$162.5066	$162.51	$162.50	$162.50
Purchase #3	$193.76	10.292%	$213.7018	$213.70	$213.70	$213.70
Purchase #4	$161.51	11.123%	$179.4748	$179.47	$179.45	$179.50
Purchase #5	$59.48	5.431%	$62.7104	$62.71	$62.70	$62.70
Purchase #6	$187.52	12.217%	$210.4293	$210.43	$210.45	$210.40
Purchase #7	$161.68	12.128%	$181.2886	$181.29	$181.30	$181.30
7 purchase totals =	$986.57		$1,081.6885	$1,081.69	$1,081.70	$1,081.70