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	$201.72	11.342%	$224.5991	$224.60	$224.60	$224.60
Purchase #2	$144.60	4.259%	$150.7585	$150.76	$150.75	$150.80
Purchase #3	$17.64	12.425%	$19.8318	$19.83	$19.85	$19.80
Purchase #4	$46.54	13.340%	$52.7484	$52.75	$52.75	$52.70
Purchase #5	$103.59	6.103%	$109.9121	$109.91	$109.90	$109.90
Purchase #6	$83.30	3.316%	$86.0622	$86.06	$86.05	$86.10
Purchase #7	$101.67	3.318%	$105.0434	$105.04	$105.05	$105.00
7 purchase totals =	$699.06		$748.9555	$748.95	$748.95	$748.90