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	$182.88	3.269%	$188.8583	$188.86	$188.85	$188.90
Purchase #2	$147.72	5.788%	$156.27	$156.27	$156.25	$156.30
Purchase #3	$14.84	9.679%	$16.2764	$16.28	$16.30	$16.30
Purchase #4	$55.77	10.441%	$61.5929	$61.59	$61.60	$61.60
Purchase #5	$234.47	7.404%	$251.8302	$251.83	$251.85	$251.80
Purchase #6	$143.93	8.748%	$156.521	$156.52	$156.50	$156.50
Purchase #7	$78.68	8.749%	$85.5637	$85.56	$85.55	$85.60
7 purchase totals =	$858.29		$916.9125	$916.91	$916.90	$917.00