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	$193.71	3.680%	$200.8385	$200.84	$200.85	$200.80
Purchase #2	$31.82	5.575%	$33.594	$33.59	$33.60	$33.60
Purchase #3	$82.53	9.395%	$90.2837	$90.28	$90.30	$90.30
Purchase #4	$197.40	9.127%	$215.4167	$215.42	$215.40	$215.40
Purchase #5	$51.55	13.357%	$58.4355	$58.44	$58.45	$58.40
Purchase #6	$185.95	10.579%	$205.6217	$205.62	$205.60	$205.60
Purchase #7	$80.64	3.611%	$83.5519	$83.55	$83.55	$83.60
7 purchase totals =	$823.60		$887.7420	$887.74	$887.75	$887.70