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	$177.39	4.757%	$185.8284	$185.83	$185.85	$185.80
Purchase #2	$78.55	3.748%	$81.4941	$81.49	$81.50	$81.50
Purchase #3	$152.79	11.780%	$170.7887	$170.79	$170.80	$170.80
Purchase #4	$143.50	5.393%	$151.239	$151.24	$151.25	$151.20
Purchase #5	$175.57	12.515%	$197.5426	$197.54	$197.55	$197.50
Purchase #6	$103.94	7.254%	$111.4798	$111.48	$111.50	$111.50
Purchase #7	$212.71	10.402%	$234.8361	$234.84	$234.85	$234.80
7 purchase totals =	$1,044.45		$1,133.2087	$1,133.21	$1,133.30	$1,133.10