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	$186.60	5.495%	$196.8537	$196.85	$196.85	$196.90
Purchase #2	$16.60	4.675%	$17.3761	$17.38	$17.40	$17.40
Purchase #3	$92.81	8.758%	$100.9383	$100.94	$100.95	$100.90
Purchase #4	$177.52	4.758%	$185.9664	$185.97	$185.95	$186.00
Purchase #5	$185.57	4.342%	$193.6274	$193.63	$193.65	$193.60
Purchase #6	$82.79	11.673%	$92.4541	$92.45	$92.45	$92.50
Purchase #7	$140.63	8.454%	$152.5189	$152.52	$152.50	$152.50
7 purchase totals =	$882.52		$939.7349	$939.74	$939.75	$939.80