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	$172.41	7.632%	$185.5683	$185.57	$185.55	$185.60
Purchase #2	$177.43	10.546%	$196.1418	$196.14	$196.15	$196.10
Purchase #3	$154.87	6.142%	$164.3821	$164.38	$164.40	$164.40
Purchase #4	$62.87	10.693%	$69.5927	$69.59	$69.60	$69.60
Purchase #5	$35.84	13.323%	$40.615	$40.62	$40.60	$40.60
Purchase #6	$224.97	9.104%	$245.4513	$245.45	$245.45	$245.50
Purchase #7	$31.32	10.262%	$34.5341	$34.53	$34.55	$34.50
7 purchase totals =	$859.71		$936.2853	$936.28	$936.30	$936.30