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	$92.32	7.306%	$99.0649	$99.06	$99.05	$99.10
Purchase #2	$153.30	7.522%	$164.8312	$164.83	$164.85	$164.80
Purchase #3	$169.41	10.455%	$187.1218	$187.12	$187.10	$187.10
Purchase #4	$213.66	5.664%	$225.7617	$225.76	$225.75	$225.80
Purchase #5	$120.68	13.594%	$137.0852	$137.09	$137.10	$137.10
Purchase #6	$154.71	7.655%	$166.5531	$166.55	$166.55	$166.60
Purchase #7	$163.45	9.815%	$179.4926	$179.49	$179.50	$179.50
7 purchase totals =	$1,067.53		$1,159.9105	$1,159.90	$1,159.90	$1,160.00