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	$62.87	13.798%	$71.5448	$71.54	$71.55	$71.50
Purchase #2	$210.88	6.383%	$224.3405	$224.34	$224.35	$224.30
Purchase #3	$109.66	4.196%	$114.2613	$114.26	$114.25	$114.30
Purchase #4	$177.93	9.219%	$194.3334	$194.33	$194.35	$194.30
Purchase #5	$22.32	10.809%	$24.7326	$24.73	$24.75	$24.70
Purchase #6	$85.27	5.613%	$90.0562	$90.06	$90.05	$90.10
Purchase #7	$246.39	13.771%	$280.3204	$280.32	$280.30	$280.30
7 purchase totals =	$915.32		$999.5892	$999.58	$999.60	$999.50