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	$185.59	11.502%	$206.9366	$206.94	$206.95	$206.90
Purchase #2	$55.89	12.423%	$62.8332	$62.83	$62.85	$62.80
Purchase #3	$82.47	8.467%	$89.4527	$89.45	$89.45	$89.50
Purchase #4	$92.62	8.614%	$100.5983	$100.60	$100.60	$100.60
Purchase #5	$15.88	10.645%	$17.5704	$17.57	$17.55	$17.60
Purchase #6	$172.94	7.677%	$186.2166	$186.22	$186.20	$186.20
Purchase #7	$219.86	11.788%	$245.7771	$245.78	$245.80	$245.80
7 purchase totals =	$825.25		$909.3849	$909.39	$909.40	$909.40