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	$88.69	13.243%	$100.4352	$100.44	$100.45	$100.40
Purchase #2	$186.25	7.587%	$200.3808	$200.38	$200.40	$200.40
Purchase #3	$166.88	12.430%	$187.6232	$187.62	$187.60	$187.60
Purchase #4	$211.54	5.467%	$223.1049	$223.10	$223.10	$223.10
Purchase #5	$74.36	10.401%	$82.0942	$82.09	$82.10	$82.10
Purchase #6	$153.60	12.458%	$172.7355	$172.74	$172.75	$172.70
Purchase #7	$98.91	3.780%	$102.6488	$102.65	$102.65	$102.60
7 purchase totals =	$980.23		$1,069.0226	$1,069.02	$1,069.05	$1,068.90