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	$68.83	3.643%	$71.3375	$71.34	$71.35	$71.30
Purchase #2	$141.94	12.766%	$160.0601	$160.06	$160.05	$160.10
Purchase #3	$164.92	12.708%	$185.878	$185.88	$185.90	$185.90
Purchase #4	$174.33	10.855%	$193.2535	$193.25	$193.25	$193.30
Purchase #5	$182.65	11.215%	$203.1342	$203.13	$203.15	$203.10
Purchase #6	$47.87	7.788%	$51.5981	$51.60	$51.60	$51.60
Purchase #7	$128.90	11.852%	$144.1772	$144.18	$144.20	$144.20
7 purchase totals =	$909.44		$1,009.4386	$1,009.44	$1,009.50	$1,009.50