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	$141.96	4.526%	$148.3851	$148.39	$148.40	$148.40
Purchase #2	$146.28	12.538%	$164.6206	$164.62	$164.60	$164.60
Purchase #3	$187.95	13.492%	$213.3082	$213.31	$213.30	$213.30
Purchase #4	$217.95	9.868%	$239.4573	$239.46	$239.45	$239.50
Purchase #5	$90.92	11.384%	$101.2703	$101.27	$101.25	$101.30
Purchase #6	$22.34	10.271%	$24.6345	$24.63	$24.65	$24.60
Purchase #7	$191.94	13.714%	$218.2627	$218.26	$218.25	$218.30
7 purchase totals =	$999.34		$1,109.9387	$1,109.94	$1,109.90	$1,110.00