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	$78.40	6.429%	$83.4403	$83.44	$83.45	$83.40
Purchase #2	$14.84	6.285%	$15.7727	$15.77	$15.75	$15.80
Purchase #3	$165.82	3.158%	$171.0566	$171.06	$171.05	$171.10
Purchase #4	$77.85	9.183%	$84.999	$85.00	$85.00	$85.00
Purchase #5	$187.49	13.416%	$212.6437	$212.64	$212.65	$212.60
Purchase #6	$109.54	12.755%	$123.5118	$123.51	$123.50	$123.50
Purchase #7	$18.39	6.281%	$19.5451	$19.55	$19.55	$19.50
7 purchase totals =	$652.33		$710.9692	$710.97	$710.95	$710.90