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	$200.27	5.323%	$210.9304	$210.93	$210.95	$210.90
Purchase #2	$233.88	12.425%	$262.9396	$262.94	$262.95	$262.90
Purchase #3	$144.35	8.538%	$156.6746	$156.67	$156.65	$156.70
Purchase #4	$17.39	7.665%	$18.7229	$18.72	$18.70	$18.70
Purchase #5	$97.45	9.624%	$106.8286	$106.83	$106.85	$106.80
Purchase #6	$136.92	5.481%	$144.4246	$144.42	$144.40	$144.40
Purchase #7	$108.31	9.651%	$118.763	$118.76	$118.75	$118.80
7 purchase totals =	$938.57		$1,019.2837	$1,019.27	$1,019.25	$1,019.20