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	$211.35	3.812%	$219.4067	$219.41	$219.40	$219.40
Purchase #2	$45.51	12.873%	$51.3685	$51.37	$51.35	$51.40
Purchase #3	$132.46	8.370%	$143.5469	$143.55	$143.55	$143.50
Purchase #4	$68.83	3.854%	$71.4827	$71.48	$71.50	$71.50
Purchase #5	$102.29	12.795%	$115.378	$115.38	$115.40	$115.40
Purchase #6	$99.96	11.318%	$111.2735	$111.27	$111.25	$111.30
Purchase #7	$145.51	9.360%	$159.1297	$159.13	$159.15	$159.10
7 purchase totals =	$805.91		$871.5860	$871.59	$871.60	$871.60