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	$76.98	12.829%	$86.8558	$86.86	$86.85	$86.90
Purchase #2	$138.55	13.847%	$157.735	$157.74	$157.75	$157.70
Purchase #3	$14.66	8.397%	$15.891	$15.89	$15.90	$15.90
Purchase #4	$14.37	6.281%	$15.2726	$15.27	$15.25	$15.30
Purchase #5	$210.40	5.836%	$222.6789	$222.68	$222.70	$222.70
Purchase #6	$183.46	8.793%	$199.5916	$199.59	$199.60	$199.60
Purchase #7	$113.42	12.342%	$127.4183	$127.42	$127.40	$127.40
7 purchase totals =	$751.84		$825.4432	$825.45	$825.45	$825.50