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	$133.50	11.307%	$148.5948	$148.59	$148.60	$148.60
Purchase #2	$137.40	8.123%	$148.561	$148.56	$148.55	$148.60
Purchase #3	$102.50	10.827%	$113.5977	$113.60	$113.60	$113.60
Purchase #4	$187.79	3.787%	$194.9016	$194.90	$194.90	$194.90
Purchase #5	$54.96	12.409%	$61.78	$61.78	$61.80	$61.80
Purchase #6	$171.86	11.677%	$191.9281	$191.93	$191.95	$191.90
Purchase #7	$194.86	13.117%	$220.4198	$220.42	$220.40	$220.40
7 purchase totals =	$982.87		$1,079.7830	$1,079.78	$1,079.80	$1,079.80