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	$55.73	11.256%	$62.003	$62.00	$62.00	$62.00
Purchase #2	$69.67	8.527%	$75.6108	$75.61	$75.60	$75.60
Purchase #3	$240.36	6.216%	$255.3008	$255.30	$255.30	$255.30
Purchase #4	$58.78	5.356%	$61.9283	$61.93	$61.95	$61.90
Purchase #5	$200.40	5.563%	$211.5483	$211.55	$211.55	$211.50
Purchase #6	$50.28	10.672%	$55.6459	$55.65	$55.65	$55.60
Purchase #7	$111.55	6.339%	$118.6212	$118.62	$118.60	$118.60
7 purchase totals =	$786.77		$840.6583	$840.66	$840.65	$840.50