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	$55.96	13.669%	$63.6092	$63.61	$63.60	$63.60
Purchase #2	$185.93	9.120%	$202.8868	$202.89	$202.90	$202.90
Purchase #3	$53.70	3.402%	$55.5269	$55.53	$55.55	$55.50
Purchase #4	$66.53	7.617%	$71.5976	$71.60	$71.60	$71.60
Purchase #5	$166.57	5.219%	$175.2633	$175.26	$175.25	$175.30
Purchase #6	$152.61	13.134%	$172.6538	$172.65	$172.65	$172.70
Purchase #7	$139.83	4.644%	$146.3237	$146.32	$146.30	$146.30
7 purchase totals =	$821.13		$887.8613	$887.86	$887.85	$887.90