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	$210.78	11.307%	$234.6129	$234.61	$234.60	$234.60
Purchase #2	$245.99	7.837%	$265.2682	$265.27	$265.25	$265.30
Purchase #3	$84.39	7.608%	$90.8104	$90.81	$90.80	$90.80
Purchase #4	$65.46	12.509%	$73.6484	$73.65	$73.65	$73.60
Purchase #5	$82.70	3.485%	$85.5821	$85.58	$85.60	$85.60
Purchase #6	$141.96	10.154%	$156.3746	$156.37	$156.35	$156.40
Purchase #7	$116.44	9.849%	$127.9082	$127.91	$127.90	$127.90
7 purchase totals =	$947.72		$1,034.2048	$1,034.20	$1,034.15	$1,034.20