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	$93.67	12.261%	$105.1549	$105.15	$105.15	$105.20
Purchase #2	$88.55	10.522%	$97.8672	$97.87	$97.85	$97.90
Purchase #3	$182.29	6.111%	$193.4297	$193.43	$193.45	$193.40
Purchase #4	$237.47	10.656%	$262.7748	$262.77	$262.75	$262.80
Purchase #5	$222.47	7.847%	$239.9272	$239.93	$239.95	$239.90
Purchase #6	$91.29	10.405%	$100.7887	$100.79	$100.80	$100.80
Purchase #7	$81.45	11.552%	$90.8591	$90.86	$90.85	$90.90
7 purchase totals =	$997.19		$1,090.8016	$1,090.80	$1,090.80	$1,090.90