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	$224.72	12.866%	$253.6325	$253.63	$253.65	$253.60
Purchase #2	$106.68	6.264%	$113.3624	$113.36	$113.35	$113.40
Purchase #3	$31.29	6.653%	$33.3717	$33.37	$33.35	$33.40
Purchase #4	$80.25	3.240%	$82.8501	$82.85	$82.85	$82.90
Purchase #5	$57.55	10.203%	$63.4218	$63.42	$63.40	$63.40
Purchase #6	$89.71	4.634%	$93.8672	$93.87	$93.85	$93.90
Purchase #7	$143.47	8.745%	$156.0165	$156.02	$156.00	$156.00
7 purchase totals =	$733.67		$796.5222	$796.52	$796.45	$796.60