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	$82.70	12.259%	$92.8382	$92.84	$92.85	$92.80
Purchase #2	$59.39	9.781%	$65.1989	$65.20	$65.20	$65.20
Purchase #3	$213.35	5.591%	$225.2784	$225.28	$225.30	$225.30
Purchase #4	$100.41	10.735%	$111.189	$111.19	$111.20	$111.20
Purchase #5	$100.75	12.651%	$113.4959	$113.50	$113.50	$113.50
Purchase #6	$58.30	7.163%	$62.476	$62.48	$62.50	$62.50
Purchase #7	$176.28	11.575%	$196.6844	$196.68	$196.70	$196.70
7 purchase totals =	$791.18		$867.1608	$867.17	$867.25	$867.20