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	$73.81	11.662%	$82.4177	$82.42	$82.40	$82.40
Purchase #2	$42.59	9.396%	$46.5918	$46.59	$46.60	$46.60
Purchase #3	$186.76	6.199%	$198.3373	$198.34	$198.35	$198.30
Purchase #4	$37.72	12.485%	$42.4293	$42.43	$42.45	$42.40
Purchase #5	$209.41	13.159%	$236.9663	$236.97	$236.95	$237.00
Purchase #6	$192.98	12.245%	$216.6104	$216.61	$216.60	$216.60
Purchase #7	$248.98	5.521%	$262.7262	$262.73	$262.75	$262.70
7 purchase totals =	$992.25		$1,086.0790	$1,086.09	$1,086.10	$1,086.00