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	$179.38	4.151%	$186.8261	$186.83	$186.85	$186.80
Purchase #2	$154.81	7.768%	$166.8356	$166.84	$166.85	$166.80
Purchase #3	$210.81	3.534%	$218.26	$218.26	$218.25	$218.30
Purchase #4	$41.79	13.534%	$47.4459	$47.45	$47.45	$47.40
Purchase #5	$201.94	12.781%	$227.75	$227.75	$227.75	$227.80
Purchase #6	$151.31	11.210%	$168.2719	$168.27	$168.25	$168.30
Purchase #7	$27.42	13.558%	$31.1376	$31.14	$31.15	$31.10
7 purchase totals =	$967.46		$1,046.5271	$1,046.54	$1,046.55	$1,046.50