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	$146.37	13.750%	$166.4959	$166.50	$166.50	$166.50
Purchase #2	$137.55	12.429%	$154.6461	$154.65	$154.65	$154.60
Purchase #3	$140.39	5.504%	$148.1171	$148.12	$148.10	$148.10
Purchase #4	$168.98	9.148%	$184.4383	$184.44	$184.45	$184.40
Purchase #5	$121.71	8.802%	$132.4229	$132.42	$132.40	$132.40
Purchase #6	$53.87	5.383%	$56.7698	$56.77	$56.75	$56.80
Purchase #7	$152.52	6.455%	$162.3652	$162.37	$162.35	$162.40
7 purchase totals =	$921.39		$1,005.2553	$1,005.27	$1,005.20	$1,005.20