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	$163.32	6.844%	$174.4976	$174.50	$174.50	$174.50
Purchase #2	$59.64	5.134%	$62.7019	$62.70	$62.70	$62.70
Purchase #3	$78.31	12.766%	$88.3071	$88.31	$88.30	$88.30
Purchase #4	$117.85	11.178%	$131.0233	$131.02	$131.00	$131.00
Purchase #5	$236.65	8.219%	$256.1003	$256.10	$256.10	$256.10
Purchase #6	$247.74	3.571%	$256.5868	$256.59	$256.60	$256.60
Purchase #7	$117.57	8.123%	$127.1202	$127.12	$127.10	$127.10
7 purchase totals =	$1,021.08		$1,096.3372	$1,096.34	$1,096.30	$1,096.30