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	$85.66	4.208%	$89.2646	$89.26	$89.25	$89.30
Purchase #2	$99.45	12.152%	$111.5352	$111.54	$111.55	$111.50
Purchase #3	$106.28	12.734%	$119.8137	$119.81	$119.80	$119.80
Purchase #4	$217.50	7.297%	$233.371	$233.37	$233.35	$233.40
Purchase #5	$35.41	9.665%	$38.8324	$38.83	$38.85	$38.80
Purchase #6	$119.80	9.265%	$130.8995	$130.90	$130.90	$130.90
Purchase #7	$188.35	11.207%	$209.4584	$209.46	$209.45	$209.50
7 purchase totals =	$852.45		$933.1748	$933.17	$933.15	$933.20