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	$202.74	12.520%	$228.123	$228.12	$228.10	$228.10
Purchase #2	$73.40	6.309%	$78.0308	$78.03	$78.05	$78.00
Purchase #3	$96.62	6.736%	$103.1283	$103.13	$103.15	$103.10
Purchase #4	$226.91	4.136%	$236.295	$236.30	$236.30	$236.30
Purchase #5	$37.92	11.786%	$42.3893	$42.39	$42.40	$42.40
Purchase #6	$72.87	11.866%	$81.5168	$81.52	$81.50	$81.50
Purchase #7	$248.38	5.315%	$261.5814	$261.58	$261.60	$261.60
7 purchase totals =	$958.84		$1,031.0646	$1,031.07	$1,031.10	$1,031.00