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	$168.60	10.230%	$185.8478	$185.85	$185.85	$185.80
Purchase #2	$81.59	13.397%	$92.5206	$92.52	$92.50	$92.50
Purchase #3	$169.72	7.591%	$182.6034	$182.60	$182.60	$182.60
Purchase #4	$230.35	4.373%	$240.4232	$240.42	$240.40	$240.40
Purchase #5	$245.98	6.438%	$261.8162	$261.82	$261.80	$261.80
Purchase #6	$168.96	11.769%	$188.8449	$188.84	$188.85	$188.80
Purchase #7	$74.78	11.760%	$83.5741	$83.57	$83.55	$83.60
7 purchase totals =	$1,139.98		$1,235.6302	$1,235.62	$1,235.55	$1,235.50