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	$250.48	13.684%	$284.7557	$284.76	$284.75	$284.80
Purchase #2	$188.65	5.781%	$199.5559	$199.56	$199.55	$199.60
Purchase #3	$49.66	3.611%	$51.4532	$51.45	$51.45	$51.50
Purchase #4	$38.61	4.542%	$40.3637	$40.36	$40.35	$40.40
Purchase #5	$163.34	5.824%	$172.8529	$172.85	$172.85	$172.90
Purchase #6	$156.51	3.843%	$162.5247	$162.52	$162.50	$162.50
Purchase #7	$224.59	3.853%	$233.2435	$233.24	$233.25	$233.20
7 purchase totals =	$1,071.84		$1,144.7496	$1,144.74	$1,144.70	$1,144.90