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	$108.47	13.532%	$123.1482	$123.15	$123.15	$123.10
Purchase #2	$86.52	6.208%	$91.8912	$91.89	$91.90	$91.90
Purchase #3	$56.57	11.103%	$62.851	$62.85	$62.85	$62.90
Purchase #4	$246.75	12.451%	$277.4728	$277.47	$277.45	$277.50
Purchase #5	$164.81	13.830%	$187.6032	$187.60	$187.60	$187.60
Purchase #6	$28.73	4.597%	$30.0507	$30.05	$30.05	$30.10
Purchase #7	$215.38	9.726%	$236.3279	$236.33	$236.35	$236.30
7 purchase totals =	$907.23		$1,009.3450	$1,009.34	$1,009.35	$1,009.40