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	$73.92	9.657%	$81.0585	$81.06	$81.05	$81.10
Purchase #2	$131.58	7.721%	$141.7393	$141.74	$141.75	$141.70
Purchase #3	$97.53	13.821%	$111.0096	$111.01	$111.00	$111.00
Purchase #4	$243.67	6.582%	$259.7084	$259.71	$259.70	$259.70
Purchase #5	$134.41	6.442%	$143.0687	$143.07	$143.05	$143.10
Purchase #6	$43.38	4.587%	$45.3698	$45.37	$45.35	$45.40
Purchase #7	$78.46	9.157%	$85.6446	$85.64	$85.65	$85.60
7 purchase totals =	$802.95		$867.5989	$867.60	$867.55	$867.60