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	$94.53	9.530%	$103.5387	$103.54	$103.55	$103.50
Purchase #2	$106.83	11.859%	$119.499	$119.50	$119.50	$119.50
Purchase #3	$115.76	10.203%	$127.571	$127.57	$127.55	$127.60
Purchase #4	$237.56	10.238%	$261.8814	$261.88	$261.90	$261.90
Purchase #5	$166.93	6.581%	$177.9157	$177.92	$177.90	$177.90
Purchase #6	$219.55	8.796%	$238.8616	$238.86	$238.85	$238.90
Purchase #7	$231.52	10.583%	$256.0218	$256.02	$256.00	$256.00
7 purchase totals =	$1,172.68		$1,285.2892	$1,285.29	$1,285.25	$1,285.30