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	$158.34	5.292%	$166.7194	$166.72	$166.70	$166.70
Purchase #2	$73.65	13.765%	$83.7879	$83.79	$83.80	$83.80
Purchase #3	$98.77	5.472%	$104.1747	$104.17	$104.15	$104.20
Purchase #4	$110.72	6.208%	$117.5935	$117.59	$117.60	$117.60
Purchase #5	$128.31	4.260%	$133.776	$133.78	$133.80	$133.80
Purchase #6	$71.48	8.838%	$77.7974	$77.80	$77.80	$77.80
Purchase #7	$76.90	7.492%	$82.6613	$82.66	$82.65	$82.70
7 purchase totals =	$718.17		$766.5102	$766.51	$766.50	$766.60