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	$108.56	13.840%	$123.5847	$123.58	$123.60	$123.60
Purchase #2	$75.27	7.372%	$80.8189	$80.82	$80.80	$80.80
Purchase #3	$248.97	5.584%	$262.8725	$262.87	$262.85	$262.90
Purchase #4	$164.79	4.679%	$172.5005	$172.50	$172.50	$172.50
Purchase #5	$104.52	10.292%	$115.2772	$115.28	$115.30	$115.30
Purchase #6	$212.90	10.331%	$234.8947	$234.89	$234.90	$234.90
Purchase #7	$96.96	10.468%	$107.1098	$107.11	$107.10	$107.10
7 purchase totals =	$1,011.97		$1,097.0583	$1,097.05	$1,097.05	$1,097.10