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	$198.38	10.423%	$219.0571	$219.06	$219.05	$219.10
Purchase #2	$70.66	4.584%	$73.8991	$73.90	$73.90	$73.90
Purchase #3	$150.90	3.742%	$156.5467	$156.55	$156.55	$156.50
Purchase #4	$211.34	12.603%	$237.9752	$237.98	$238.00	$238.00
Purchase #5	$62.61	8.493%	$67.9275	$67.93	$67.95	$67.90
Purchase #6	$158.82	13.769%	$180.6879	$180.69	$180.70	$180.70
Purchase #7	$58.41	5.207%	$61.4514	$61.45	$61.45	$61.50
7 purchase totals =	$911.12		$997.5449	$997.56	$997.60	$997.60