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	$186.88	13.593%	$212.2826	$212.28	$212.30	$212.30
Purchase #2	$144.43	4.177%	$150.4628	$150.46	$150.45	$150.50
Purchase #3	$43.59	12.749%	$49.1473	$49.15	$49.15	$49.10
Purchase #4	$200.52	12.389%	$225.3624	$225.36	$225.35	$225.40
Purchase #5	$77.68	6.866%	$83.0135	$83.01	$83.00	$83.00
Purchase #6	$98.84	12.429%	$111.1248	$111.12	$111.10	$111.10
Purchase #7	$247.46	13.763%	$281.5179	$281.52	$281.50	$281.50
7 purchase totals =	$999.40		$1,112.9113	$1,112.90	$1,112.85	$1,112.90