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	$60.66	3.801%	$62.9657	$62.97	$62.95	$63.00
Purchase #2	$117.38	8.676%	$127.5639	$127.56	$127.55	$127.60
Purchase #3	$117.76	4.744%	$123.3465	$123.35	$123.35	$123.30
Purchase #4	$50.90	12.856%	$57.4437	$57.44	$57.45	$57.40
Purchase #5	$228.27	3.764%	$236.8621	$236.86	$236.85	$236.90
Purchase #6	$36.86	5.585%	$38.9186	$38.92	$38.90	$38.90
Purchase #7	$63.63	7.709%	$68.5352	$68.54	$68.55	$68.50
7 purchase totals =	$675.46		$715.6357	$715.64	$715.60	$715.60