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	$78.94	5.562%	$83.3306	$83.33	$83.35	$83.30
Purchase #2	$173.47	8.328%	$187.9166	$187.92	$187.90	$187.90
Purchase #3	$240.72	10.690%	$266.453	$266.45	$266.45	$266.50
Purchase #4	$57.34	9.767%	$62.9404	$62.94	$62.95	$62.90
Purchase #5	$135.72	5.212%	$142.7937	$142.79	$142.80	$142.80
Purchase #6	$203.42	3.280%	$210.0922	$210.09	$210.10	$210.10
Purchase #7	$141.78	7.123%	$151.879	$151.88	$151.90	$151.90
7 purchase totals =	$1,031.39		$1,105.4055	$1,105.40	$1,105.45	$1,105.40