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	$188.68	12.562%	$212.382	$212.38	$212.40	$212.40
Purchase #2	$189.26	12.809%	$213.5023	$213.50	$213.50	$213.50
Purchase #3	$65.93	10.225%	$72.6713	$72.67	$72.65	$72.70
Purchase #4	$56.65	10.236%	$62.4487	$62.45	$62.45	$62.40
Purchase #5	$208.61	6.825%	$222.8476	$222.85	$222.85	$222.80
Purchase #6	$53.84	10.804%	$59.6569	$59.66	$59.65	$59.70
Purchase #7	$156.64	12.846%	$176.762	$176.76	$176.75	$176.80
7 purchase totals =	$919.61		$1,020.2708	$1,020.27	$1,020.25	$1,020.30