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	$102.91	6.312%	$109.4057	$109.41	$109.40	$109.40
Purchase #2	$83.94	4.262%	$87.5175	$87.52	$87.50	$87.50
Purchase #3	$149.27	4.182%	$155.5125	$155.51	$155.50	$155.50
Purchase #4	$160.91	12.510%	$181.0398	$181.04	$181.05	$181.00
Purchase #5	$247.54	13.540%	$281.0569	$281.06	$281.05	$281.10
Purchase #6	$145.57	7.125%	$155.9419	$155.94	$155.95	$155.90
Purchase #7	$120.94	8.744%	$131.515	$131.52	$131.50	$131.50
7 purchase totals =	$1,011.08		$1,101.9893	$1,102.00	$1,101.95	$1,101.90