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	$155.46	4.611%	$162.6283	$162.63	$162.65	$162.60
Purchase #2	$222.80	6.641%	$237.5961	$237.60	$237.60	$237.60
Purchase #3	$90.70	9.754%	$99.5469	$99.55	$99.55	$99.50
Purchase #4	$82.93	3.189%	$85.5746	$85.57	$85.55	$85.60
Purchase #5	$164.88	6.485%	$175.5725	$175.57	$175.55	$175.60
Purchase #6	$166.63	10.435%	$184.0178	$184.02	$184.00	$184.00
Purchase #7	$26.65	3.655%	$27.6241	$27.62	$27.60	$27.60
7 purchase totals =	$910.05		$972.5603	$972.56	$972.50	$972.50