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	$66.79	5.670%	$70.577	$70.58	$70.60	$70.60
Purchase #2	$187.75	6.827%	$200.5677	$200.57	$200.55	$200.60
Purchase #3	$193.86	7.817%	$209.014	$209.01	$209.00	$209.00
Purchase #4	$162.97	10.694%	$180.398	$180.40	$180.40	$180.40
Purchase #5	$92.85	13.701%	$105.5714	$105.57	$105.55	$105.60
Purchase #6	$241.88	13.259%	$273.9509	$273.95	$273.95	$274.00
Purchase #7	$53.68	3.681%	$55.656	$55.66	$55.65	$55.70
7 purchase totals =	$999.78		$1,095.7350	$1,095.74	$1,095.70	$1,095.90