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	$99.96	8.386%	$108.3426	$108.34	$108.35	$108.30
Purchase #2	$151.45	4.841%	$158.7817	$158.78	$158.80	$158.80
Purchase #3	$117.39	8.649%	$127.5431	$127.54	$127.55	$127.50
Purchase #4	$190.82	3.254%	$197.0293	$197.03	$197.05	$197.00
Purchase #5	$194.98	5.553%	$205.8072	$205.81	$205.80	$205.80
Purchase #6	$159.76	12.525%	$179.7699	$179.77	$179.75	$179.80
Purchase #7	$133.69	12.405%	$150.2742	$150.27	$150.25	$150.30
7 purchase totals =	$1,048.05		$1,127.5480	$1,127.54	$1,127.55	$1,127.50