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	$177.59	5.230%	$186.878	$186.88	$186.90	$186.90
Purchase #2	$66.79	8.697%	$72.5987	$72.60	$72.60	$72.60
Purchase #3	$80.28	4.135%	$83.5996	$83.60	$83.60	$83.60
Purchase #4	$95.70	7.653%	$103.0239	$103.02	$103.00	$103.00
Purchase #5	$234.91	11.130%	$261.0555	$261.06	$261.05	$261.10
Purchase #6	$127.96	7.281%	$137.2768	$137.28	$137.30	$137.30
Purchase #7	$148.81	13.257%	$168.5377	$168.54	$168.55	$168.50
7 purchase totals =	$932.04		$1,012.9702	$1,012.98	$1,013.00	$1,013.00